NATIONAL CENTER FOR HEALTH STATISTICS 

Vital and Health Statistics 

Series 3, Number 42 June 2018 

98.1 (0.93) 

99.5 (0.26) 

98.7 (0.75) 

99.3 (0.73) 

98.4 (1.49) 

98.4 (1.58) 

94.7 (1.95) 

98.6 (1.30) 

92.4 (2.88) 

92.5 (2.46) 

96.7 (2.48) 

91.8 (3.61) 

17.0 (0.46) 

16.7 (0.55) 

16.8 (1.01) 

11.8 (2.48) 

20.0 (1.88) 

12.9 (1.13) 

8.7 (1.26) 

7.3 (2.20) 

17.1 (4.43) 

14.5 (3.05) 

7.7 (2.11) 

3.8 (0.64) 

4.7 (1.03) 

*2.4 (1.00) 

84.5 (7.72) 

*8.3 (3.48) 

13.6 (2.00) 

*3.9 (1.52) 

17.5 (2.81) 

*19.2 (7.52) 

*18.5 (6.70) 

*17.1 (4.85) 

96.9 (0.21)

97.0 (0.24)

97.2 (0.44)

96.8 (1.27)

95.2 (0.88)

96.7 (0.78)

99.3 (0.29)

94.8 (1.66)

95.6 (1.39)

97.5 (1.40)

93.1 (2.60)

98.1 (0.93)

99.5 (0.26)

98.7 (0.75)

99.3 (0.73)

98.4 (1.49)

98.4 (1.58)

94.7 (1.95)

98.6 (1.30)

92.4 (2.88)

92.5 (2.46)

96.7 (2.48)

91.8 (3.61)

97.0 (0.24)

97.2 (0.44)

96.8 (1.27)

95.2 (0.88)

96.7 (0.78)

99.3 (0.29)

94.8 (1.66)

95.6 (1.39)

97.5 (1.40)

93.1 (2.60)

98.1 (0.93)

99.5 (0.26)

98.7 (0.75)

99.3 (0.73)

98.4 (1.49)

98.4 (1.58)

94.7 (1.95)

98.6 (1.30)

92.4 (2.88)

92.5 (2.46)

96.7 (2.48)

91.8 (3.61)

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Centers for Disease Control and Prevention 

National Center for Health Statistics 

Excess Deaths Associated With 

Underweight, Overweight, and 

Obesity: An Evaluation of 

Potential Bias 

Analytical and Epidemiological Studies 
Copyright information

All material appearing in this report is in the public domain and may be reproduced or 

copied without permission; citation as to source, however, is appreciated. 

Suggested citation

Flegal KM, Graubard BI, Williamson DF, Gail MH. Excess deaths associated with 

underweight, overweight, and obesity: An evaluation of potential bias. National Center for 

Health Statistics. Vital Health Stat 3(42). 2018. 

Library of Congress Cataloging-in-Publication Data

Names: National Center for Health Statistics (U.S.), issuing body. 

Title: Excess deaths associated with underweight, overweight, and obesity : 

 an evaluation of potential bias. 

Other titles: Vital & health statistics. Series 3, Analytical and 

 epidemiological studies ; no. 42. | DHHS publication ; no. 2018-1426. 

Description: Washington, DC : U.S. Department of Health and Human Services, 

 Centers for Disease Control and Prevention, National Center for Health 

 Statistics, June 2018. | Series: Vital and health statistics. Series 3, 

 Analytical and epidemiological studies ; number 42 | Series: DHHS 

 publication ; no. 2018-1426 | Includes bibliographical references. 

Identifiers: LCCN 2018022521 | ISBN 0840606907 (pbk.) 

Subjects: | MESH: Thinness--mortality | Bias | Overweight--mortality | 

 Obesity--mortality | Body Mass Index | United States | Statistics 

Classification: LCC RA645.N87 | NLM W2 A N148vc no.42 2018 | DDC 

362.1963/9--dc23 

LC record available at https://lccn.loc.gov/2018022521 

For sale by the U.S. Government Printing Office 

Superintendent of Documents 

Mail Stop: SSOP 

Washington, DC 20402–9328 

Printed on acid-free paper. 
Excess Deaths Associated With 

Underweight, Overweight, and 

Obesity: An Evaluation of 

Potential Bias

Data from the National Health and Nutrition Examination 

Survey

NATIONAL CENTER FOR HEALTH STATISTICS

Vital and Health Statistics

Series 3, Number 42 June 2018

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Center for Health Statistics

Hyattsville, Maryland

June 2018

DHHS Publication No. 2018–1426
National Center for Health Statistics

Charles J. Rothwell, M.S., M.B.A., Director 

Jennifer H. Madans, Ph.D., Associate Director for Science 

Division of Health and Nutrition Examination Surveys

Kathryn S. Porter, M.D., M.S., Director 

Ryne Paulose-Ram, Ph.D., Associate Director for Science 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Series 3, Number 42 v NATIONAL CENTER FOR HEALTH STATISTICS 

Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Methods of Previous Paper. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Controlling for Confounding Factors by Adjustment or Exclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Evaluation of Potential Bias. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Data Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Health Status Reports. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Health Status Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Effects of Age at Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Proportions Excluded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Relative Risk of Mortality Associated With Underweight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Relative Risk of Mortality Associated With Overweight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Relative Risk of Mortality Associated With Obesity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Proportions Excluded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Tables

A. Adjusted relative risk (95% confidence interval) of mortality, by age group, survey, and body mass index

category: National Health and Nutrition Examination Survey, United States, 1971–1994 . . . . . . . . . . . . . . . . . . 4

B. Adjusted relative risk (95% confidence interval) of mortality for respondents with weight change of 2 kg

or less between 1971–1975 and 1982–1984, by age group and body mass index category: National

Health and Nutrition Examination Survey, United States, 1971–1975 and National Health and Nutrition

Examination Survey I Epidemiologic Follow-up Study, 1982–1984 and 1992 . . . . . . . . . . . . . . . . . . . . . . . . . 5

C. Adjusted relative risk (95% confidence interval) of mortality before and after excluding deaths occurring

in the first 3 or 5 years after baseline, by age group and body mass index category: National Health and

Nutrition Examination Survey, United States, 1971–1994. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

D. Adjusted relative risk (95% confidence interval) of mortality associated with self-reported health status,

by age group and survey: National Health and Nutrition Examination Survey, United States, 1971–1994 . . . . . . . . . 6

E. Adjusted relative risk (95% confidence interval) of mortality for self-reported good, fair, or poor health

relative to self-reported excellent or very good health, by age group and survey: National Health and

Nutrition Examination Survey, United States, 1971–1994. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

F. Adjusted relative risk (95% confidence interval) of mortality, by age group, body mass index category, and

selected exclusionary criteria: National Health and Nutrition Examination Survey, United States, 1971–1994 . . . . . . 7

G. Adjusted relative risk (95% confidence interval) of mortality associated with five categories of

physician-evaluated health status, by age group and model: National Health and Nutrition Examination

Survey, United States, 1988–1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

H. Adjusted relative risk (95% confidence interval) of mortality for two categories of physician-evaluated

health status, by age group and model: National Health and Nutrition Examination Survey, United States,

1988–1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
NATIONAL CENTER FOR HEALTH STATISTICS vi Series 3, Number 42 

 

 

Contents—Con. 

J. Adjusted relative risk (95% confidence interval) of mortality before and after stratifying by 

physician-evaluated health status and selected exclusionary criteria, by age group and body mass index 

category: National Health and Nutrition Examination Survey, United States, 1988–1994 . . . . . . . . . . . . . . . . . . 8

K. Adjusted relative risk (95% confidence interval) of mortality after stratifying by self-reported health 

status and excluding respondents with involuntary weight loss in 6 months prior to baseline: National 

Health and Nutrition Examination Survey, United States, 1976–1980 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

M. Adjusted relative risk (95% confidence interval) of mortality for persons aged 70 and over, by survey, 

body mass index category, and age at measurement of weight and height: National Health and Nutrition 

Examination Survey, United States, 1971–1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

N. Percentage of sample and percentage of deaths remaining before and after selected exclusionary criteria 

were applied, by age group and survey: National Health and Nutrition Examination Survey, 

United States, 1971–1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Previous analyses of mortality data from the National 

Health and Nutrition Examination Survey published in 

2005 found that relative to the normal weight category 

of body mass index (BMI), defined as a BMI of 18.5–24.9, 

underweight (BMI less than 18.5) and obesity (BMI 

greater than or equal to 30) were associated with excess 

mortality, and overweight (BMI 25–29.9) was associated 

with reduced mortality, after adjusting for sex, smoking 

status, race–ethnicity group, and alcohol consumption. 

Possible sources of bias in those analyses include 

residual confounding due to imperfect adjustment for 

smoking and prevalent illness at baseline. This report 

presents an evaluation of these sources of bias. 

The relative risks associated with BMI categories were 

calculated both before and after exclusions based on 

self-reported health status, physician-evaluated health 

status, smoking, early death, and weight stability. 

Additional analyses examined the effects of using BMI 

measured after age 70. 

No systematic or large effects of exclusions on the 

magnitude or direction of the relative risks were 

observed. Underweight was associated with elevated 

risk and overweight with decreased risk relative to the 

normal weight category, even after exclusions based on 

smoking, health status, early death, and weight stability. 

Applying these exclusionary criteria simultaneously 

excluded up to 85% of the original sample and 92% of 

the deaths. 

These analyses of the effects of exclusions and 

stratification by health status do not suggest that the 

2005 results were affected by large or systematic biases 

from residual confounding due to smoking, prevalent 

illness at baseline, or illness-induced weight loss. 

Keywords: mortality • epidemiological methods • 

self-reported health • National Health and Nutrition 

Examination Survey

Excess Deaths Associated With 

Underweight, Overweight, and Obesity: 

An Evaluation of Potential Bias 

by Katherine M. Flegal, Ph.D., National Center for Health Statistics; Barry I. Graubard, Ph.D., National Cancer 

Institute; David F. Williamson, Ph.D., National Center for Chronic Disease Prevention and Health Promotion; 

and Mitchell H. Gail, M.D., Ph.D., National Cancer Institute

Abstract 

Objectives Results 

Conclusions 

Methods 

Introduction 

As the prevalence of obesity has increased over time in the 

United States (1,2), concern over the association between 

body weight and excess mortality also increased. In 2005, an 

analysis of estimated excess deaths, relative to the normal 

weight category (body mass index [BMI] 18.5–24.9), that 

were associated with underweight (BMI less than 18.5), 

overweight (BMI 25.0–29.9), and obesity (BMI greater than 

or equal to 30) in U.S. adults in 2000 was published (3). 

Both underweight and obesity, particularly higher levels of 

obesity, were associated with increased mortality relative 

to the normal weight category. Obesity was estimated to 

be associated with 111,909 excess deaths (95% confidence 

interval [CI]: 53,754 to 170,064) in 2000 relative to the 

normal weight category, and underweight with 33,746 

excess deaths (95% CI: 15,726 to 51,766). Overweight was 

associated with reduced mortality (−86,094 deaths; 95% CI: 

−161,223 to −10,966). This report evaluates several potential 

sources of bias in that analysis. 

Methods of Previous Paper 

The published analysis (3) used all of the then-available 

mortality data from the National Health and Nutrition 

Examination Surveys (NHANES), including the first, second, 

and third NHANES (NHANES I, 1971–1975; NHANES II, 

1976–1980; and NHANES III, 1988–1994). A statistical 

approach derived from the Gail model's methods for 

predicting breast cancer risk was used (4,5). BMI was 

calculated as weight divided by height squared (kg/m2

) and 

grouped into categories of underweight (BMI less than 18.5), 

normal weight (BMI 18.5–24.9), overweight (BMI 25–29.9), 

grade 1 obesity (BMI 30–34.9), and grades 2 and 3 obesity 

Series 3, Number 42 1 NATIONAL CENTER FOR HEALTH STATISTICS 
(BMI greater than or equal to 35), according to categories 

used by the National Heart, Lung, and Blood Institute (6) and 

the World Health Organization (7). The normal weight 

category was used as the reference category. The relative 

risks (hazard ratios) of mortality from the combined NHANES 

I, II, and III data were estimated from proportional hazards 

survival models that used age as the time metric (8,9). 

Because the proportional hazards assumption was not 

always met, data were stratified into three age categories: 

25–59, 60–69, and 70 and over. Because age was used as the 

time metric, a participant might be included in more than 

one of these groups. For example, a participant who was 

examined at age 59 at baseline but survived to age 70 or 

over would be included in age-specific analyses for all three 

groups. 

The statistical models included the following covariates 

measured at baseline: sex, smoking (never, former, or 

current), race–ethnicity group (white, black, or other), and 

alcohol consumption, in grams per day (none, less than 0.07, 

0.07 to less than 0.35, or greater than or equal to 0.35). The 

relative risks for BMI and all other covariates were applied 

to the joint distribution of BMI and other covariates in the 

population, as estimated from NHANES 1999–2002, to 

estimate attributable fractions. Finally, those fractions were 

applied to the total number of deaths in the United States in 

2000 (from vital statistics data) for persons of the same ages. 

All analyses included sample weights that accounted for 

the unequal probabilities of selection due to oversampling 

and nonresponse. All variance calculations incorporated 

the sample weights and accounted for the complex sample 

design. Standard errors were calculated by applying a delta 

method for complex sample designs. This method takes into 

account a) sampling variability in estimating the relative risks 

and the joint distribution of BMI and the other covariates, 

and b) additional variability due to the complex sample 

designs of NHANES. 

Controlling for Confounding Factors by 

Adjustment or Exclusion 

Adjusting relative risk estimates for confounding factors 

(e.g., age and smoking) that are associated with both 

obesity and mortality is important (10,11). However, 

when relative risks are adjusted for confounding factors, 

it is also necessary to use properly adjusted estimators of 

attributable fractions to avoid bias (12,13). The method used 

for this analysis accounted for confounding and allowed 

for effect modification across age strata. Because the goal 

was to make estimates for the entire U.S. adult population 

within each age stratum, rather than for selected subgroups, 

all participants were included. This approach adjusted 

for confounding by calculating the hazard ratios for BMI 

categories and the confounding factors, and applying these 

hazard ratios to the then-current distribution of BMI and the 

confounding factors in the U.S. population. 

For studies estimating the relative risks of mortality 

associated with different levels of BMI, it is sometimes 

recommended that rather than using statistical adjustments 

for or stratification by confounding factors, participants with 

certain characteristics simply be excluded from the analytic 

sample (14,15). This is believed to avoid possible biases due 

to illness-induced weight loss or residual confounding by 

smoking or prevalent illness at baseline. 

For example, cigarette smoking is associated both with lower 

body weight (16,17) and increased mortality (18). If smoking 

were not completely adjusted for, this could overestimate 

the relative risk associated with underweight, and 

underestimate the relative risk associated with overweight 

and obesity with respect to normal weight. One approach 

to this problem is to statistically adjust for smoking status 

(19,20). An alternative approach is to exclude all current 

and former smokers and calculate relative risks only for 

the remaining never smokers (14). It has been stated that, 

“the best way to assess the impact of overweight on risk 

of mortality is simply to exclude current and past smokers” 

(14). This is, in effect, a method of adjusting for confounding 

by calculating relative risks for only the unexposed level of 

the confounder. 

The actual exclusions used to control for the effects of 

smoking, prevalent illness, and illness-induced weight loss 

vary considerably from study to study but can be grouped 

into four main types. First, current and former smokers 

may be excluded (21–25). Second, deaths occurring within 

the first few years after the baseline examination may 

be excluded to eliminate those with prevalent illness at 

baseline from the analysis. These “early death” exclusions 

may eliminate the first 5 years (26), 4 years (24), or 2 years 

(21) of deaths. A third type of exclusion is to exclude from 

analysis those with various self-reported health conditions 

at baseline. Common exclusions include those with selfreported cancer or cardiovascular disease at baseline (26); 

those with self-reported history of cancer, heart disease, 

stroke, respiratory disease, or any current illness (22); or 

those with self-reported heart disease, cancer, stroke, or 

poor health (25). A fourth type of exclusion involves weight 

stability. Exclusions of this type remove from the analytic 

sample those with a self-reported weight change of 4.5 kg 

or more over the first 5 years of the study (26), those with a 

self-reported weight loss of 4.5 kg or more in the year before 

baseline (22), those with a self-reported weight loss of 4.5 kg 

or more in the 2 years before baseline (25), and those with a 

self-reported weight gain or loss of 4 kg or more in the first 

4 years after baseline (24). These exclusions are intended 

to eliminate from the analysis people who may have 

experienced recent weight loss due to illness, although 

people who report weight gain after baseline are sometimes 

also excluded (24). 

NATIONAL CENTER FOR HEAL CENTER FOR HEALTH STATISTICS 2 Series 3, Number 42 Series 3, Number 42 
Evaluation of Potential Bias 

To assess the possibility that systematic biases related 

to smoking or prevalent illness at baseline had affected 

the estimates, relative risks within subgroups based on 

exclusionary criteria, alone and in combination, were 

examined. The previous analyses by Flegal et al. (3) found 

that underweight was associated with a relative risk greater 

than 1, overweight with a relative risk less than 1, and obesity 

with a relative risk greater than 1. If these results had been 

biased by illness-induced weight loss, prevalent disease at 

baseline, or residual confounding due to incomplete control 

for cigarette smoking, analyses excluding participants with 

these factors would be expected to show a relative risk 

associated with underweight close to or under 1, a relative 

risk associated with overweight greater than 1, and a relative 

risk associated with obesity higher than previously observed. 

Flegal et al. (3) reported the relative risks from analyses 

limited to never smokers, and described the results from a) 

analyses that excluded the first 3 or 5 years of deaths, and 

b) analyses (for NHANES I only) that were limited to persons 

whose measured weight had not changed by more than 2

kg over an approximately 10-year period. These exclusions 

were done separately and not in combination. None of the 

exclusions described in the published article resulted in any 

large or systematic differences in estimates of relative risk 

compared with the full-sample estimates without exclusions. 

This report presents detailed results of the effects of 

exclusions on relative risk estimates. The effects of exclusions 

based on health status are presented, as well as the effects 

of simultaneous exclusions of several different factors. Also 

discussed are some limitations of the exclusionary approach 

when attempting to estimate the absolute number of 

excess deaths associated with body weight in the total U.S. 

population. 

Methods 

Data Sources 

The NHANES program of the National Center for Health 

Statistics (NCHS) includes a series of cross-sectional, 

nationally representative health examination surveys 

beginning in 1960. In each survey, a nationally representative 

sample of the U.S. civilian noninstitutionalized population 

was selected using a complex, stratified, multistage 

probability cluster sampling design. Previous national 

surveys include the first National Health Examination Survey 

(NHES I, 1960–1962) and the first, second, and third National 

Health and Nutrition Examination Surveys (NHANES I, 

1971–1975; NHANES II, 1976–1980; and NHANES III, 

1988–1994) (27–30). Beginning in 1999, NHANES became 

a continuous survey. The procedures followed to select the 

samples and conduct the interviews and examinations were 

similar across surveys, each of which includes an interview 

in the household and a physical examination in a mobile 

examination center. 

At the time of the previous analysis (3), data on subsequent 

mortality among survey participants were available for three 

of these surveys: NHANES I, NHANES II, and NHANES III. The 

NHANES I Epidemiologic Follow-up Study (NHEFS) consisted 

of several waves of follow-up (31,32). Participants were 

recontacted, and medical records and death certificates 

were obtained. In the NHANES II Mortality Study, vital status 

for NHANES II participants was assessed by searching the 

National Death Index and the Social Security Administration 

Death Master File for deaths occurring in the United States 

(33). Causes of death were obtained from the NCHS Multiple 

Cause of Death file or from death certificates. Similar 

procedures were followed for the NHANES III Mortality 

Study. Mortality data were available through 1992 for both 

NHANES I and NHANES II, and through 2000 for NHANES III. 

The 1982–1984 follow-up in NHEFS included a measurement 

of weight as part of a home examination. Thus, for NHANES I 

only, measured weights are available at two different time 

points. This report primarily examines the relative risks for 

mortality in NHANES I from baseline (1971–1975), with 

follow-up through 1992. Several analyses also estimate 

the relative risks for NHANES I from baseline (1971–1975) 

though the 1982–1984 follow-up, and the relative risk 

from the 1982–1984 follow-up through 1992. For analyses 

of data from the 1982–1984 follow-up through 1992, BMI 

was calculated from weight measured in the 1982–1984

follow-up and height measured at baseline. 

Health Status Reports 

In each of the NHANES surveys, respondents were asked to 

evaluate their own health as excellent, very good, good, fair, 

or poor. These responses were grouped into two categories 

(excellent or very good health, and good, fair, or poor health) 

and results were stratified by these two levels of health 

status. 

In NHANES III only, the examining physician at baseline was 

also asked to rate the respondent’s overall health condition 

using the same five categories of excellent, very good, good, 

fair, or poor. Many large epidemiologic cohort studies do 

not include a baseline evaluation by a physician. Physicianevaluated health condition was grouped into two categories: 

a) excellent or very good health and b) good, fair, or poor 

health. 

In NHANES III, physician-evaluated health status was 

compared with self-reported health status. Additionally, 

both physician-evaluated health status and self-reported 

health status were compared against reported history of 

cancer (other than skin cancer), congestive heart failure, 

stroke, heart attack, diabetes, and emphysema. 

In NHANES III, respondents were asked to report their 

current weight at baseline and their weight 10 years ago. 

Series 3, Number 42 3 NATIONAL CENTER FOR HEALTH STATISTICS 
For some analyses of NHANES III data, respondents who reported any net weight 

loss greater than 2.5 kg over the 10 years before baseline, based on the two selfreported measurements, were excluded. 

In NHANES II, participants were asked if they had had unexplained weight loss 

in the previous 6 months. This question should identify respondents with recent 

weight loss due to illness. Some analyses for NHANES II were limited to those 

participants who did not report any unexplained weight loss. 

Various combinations of these exclusions were examined. To have sufficient deaths 

for analyses in younger age groups, the sample was divided into two age groups: 

under 70 and 70 and over. A person who was examined at an age under 70 at 

baseline but survived to age 70 or over would be included in age-specific analyses 

for both groups, because age was used as the time metric. 

Table A. Adjusted relative risk (95% confidence interval) of mortality, by 

age group, survey, and body mass index category: National Health and 

Nutrition Examination Survey I, II, and III, 1971–1994 

Survey and body mass 

index category 25–59 years 60–69 years 70 years and over 

NHANES I 

1971–1975 to 1982–1984 

Under 18.5 2.09 (0.98–4.45) 2.71 (1.52–4.83) 2.96 (1.90–4.61) 1

18.5–24.9 1 1 1 

25.0–29.9 0.95 (0.63–1.42) 0.99 (0.70–1.40) 0.79 (0.67–0.94) 

30.0–34.9 1.41 (0.86–2.32) 1.51 (0.95–2.39) 1.11 (0.84–1.47) 

35.0 and over 2.28 (1.18–4.40) 1.67 (0.86–3.24) 1.62 (1.05–2.50) 

NHANES I 

1982–1984 to 19922

Under 18.5 1.85 (0.73–4.72) 1.97 (0.82–4.76) 1.78 (1.26–2.53) 1

18.5–24.9 1 1 1 

25.0–29.9 0.76 (0.45–1.28) 0.74 (0.51–1.07) 0.89 (0.73–1.08) 

30.0–34.9 1.36 (0.80–2.30) 1.11 (0.73–1.71) 1.03 (0.83–1.28) 

35.0 and over 0.96 (0.47–1.98) 0.70 (0.29–1.68) 1.33 (0.84–2.10) 

NHANES II 

1976–1980 to 1992 

Under 18.5 0.85 (0.36–1.99) 1.47 (0.74–2.93) 1.50 (1.06–2.11) 1

18.5–24.9 1 1 1 

25.0–29.9 0.71 (0.45–1.13) 0.80 (0.63–1.02) 0.86 (0.75–0.99) 

30.0–34.9 0.71 (0.41–1.22) 0.95 (0.65–1.40) 1.11 (0.86–1.42) 

35.0 and over 1.18 (0.75–1.87) 1.29 (0.85–1.97) 0.98 (0.75–1.29) 

NHANES III 

1988–1994 to 2000 

Under 18.5 1.35 (0.41–4.38) 3.18 (1.78–5.68) 1.67 (1.21–2.30) 1

18.5–24.9 1 1 1 

25.0–29.9 0.86 (0.55–1.34) 1.01 (0.68–1.48) 0.89 (0.74–1.06) 

30.0–34.9 1.26 (0.67–2.37) 0.94 (0.56–1.57) 0.91 (0.74–1.11) 

35.0 and over 1.64 (0.90–2.97) 1.66 (0.83–3.32) 0.98 (0.66–1.46) 

1

Reference category. 

2

Body mass index was calculated using height measured in 1971–1975 and weight measured in 

1982–1984. 

NOTES: NHANES is National Health and Nutrition Examination Survey. Relative risks are adjusted for 

sex, smoking status, race–ethnicity group, and alcohol consumption. Body mass index is calculated as 

weight in kilograms (kg) divided by height in meters squared (m2

). 

SOURCES: NCHS, NHANES, 1971–1994, and NHANES I Epidemiologic Follow-up Study, 1982–1992. 

Results 

Separate relative risks for the two 

parts of NHANES I and relative risks for 

NHANES II and III are shown in Table A. 

To examine whether the higher relative 

risks in NHANES I might be due to the 

longer follow-up in NHANES I, the 

relative risks from the first phase of 

NHANES I through the 1982–1984

follow-up were compared with the 

relative risks from NHANES II and 

III. Thus, the follow-up period was 

similar for all surveys (10 years for 

NHANES I, 14 years for NHANES II, and 

9 years for NHANES III). The NHANES I 

relative risks over the first 10 years of 

follow-up were higher in almost every 

BMI–age subgroup compared with the 

relative risks from the other surveys. 

Thus, even after controlling for length 

of follow-up, NHANES I tended to have 

higher relative risks than the other 

surveys. 

As also displayed in Table A, in NHANES 

I, the relative risks through 1992

associated with weights measured in 

the 1982–1984 follow-up were lower 

in almost all subgroups than the 

relative risks from 1971–1975 through 

the 1982–1984 follow-up, suggesting a 

possible decrease in relative risks over 

time, although the differences were 

small. 

To assess the longer-term effects of 

a given weight, excluding possible 

effects of major weight gains or losses, 

the NHANES I analyses were repeated 

for a subgroup of participants whose 

weight had not changed by more than 

2 kg between baseline (1971–1975) 

and 1982–1984, looking at mortality 

from the 1982–1984 follow-up through 

1992. In these analyses, the relative 

risks for this subgroup in NHANES I 

(Table B) did not differ systematically 

from those for the whole NHANES I 

sample over the same time period 

from the 1982–1984 follow-up through 

1992 (Table A), and differences were 

slight. Overweight (BMI 25–29.9) that 

had persisted for at least 10 years was 

still associated with no excess risk, and 

underweight was still associated with 

an increased relative risk. 

NATIONAL CENTER FOR HEALTH STATISTICS 4 Series 3, Number 42 
 

 

Table B. Adjusted relative risk (95% confidence interval) of mortality for 

respondents with weight change of 2 kg or less between 1971–1975 and 

1982–1984, by age group and body mass index category: National Health 

and Nutrition Examination Survey, 1971–1975, and National Health and 

Nutrition Examination Survey I Epidemiologic Follow-up Study, 

1982–1984 and 1992 

Body mass index category 25–59 years 60–69 years 70 years and over 

Under 18.5 2.41 (0.95–6.13) 1.23 (0.31–4.85) 2.16 (0.89–5.28) 1

18.5–24.9 1 1 1 

25.0–29.9 0.52 (0.18–1.50) 1.00 (0.42–2.37) 1.00 (0.73–1.37) 

30.0–34.9 0.59 (0.14–2.57) 0.91 (0.34–2.44) 1.23 (0.72–2.08) 

35.0 and over 0.73 (0.14–3.98) 0.60 (0.10–3.68) 2.36 (0.73–7.56) 

1

Reference category. 

NOTES: Relative risks are adjusted for sex, smoking status, race–ethnicity group, and alcohol 

consumption. Body mass index is calculated as weight in kilograms (kg) divided by height in meters 

squared (m2

). 

SOURCES: NCHS, National Health and Nutrition Examination Survey, 1971–1975, and National Health 

and Nutrition Examination Survey I Epidemiologic Follow-up Study, 1982–1984 and 1992. 

Table C. Adjusted relative risk (95% confidence interval) of mortality 

before and after excluding deaths occurring in the first 3 or 5 years after 

baseline, by age group and body mass index category: National Health 

and Nutrition Examination Survey, 1971–1994 

Body mass index category 25–59 years 60–69 years 70 years and over 

Including all deaths 

Under 18.5 1.38 (0.82–2.32) 2.30 (1.70–3.13) 1.69 (1.38–2.07) 1

18.5–24.9 1 1 1 

25.0–29.9 0.83 (0.65–1.06) 0.95 (0.80–1.13) 0.91 (0.83–1.01) 

30.0–34.9 1.20 (0.84–1.72) 1.13 (0.89–1.42) 1.03 (0.91–1.17) 

35.0 and over 1.83 (1.27–2.62) 1.63 (1.16–2.30) 1.17 (0.94–1.47) 

Excluding deaths 

In the frst 3 years after baseline: 

Under 18.5 1.29 (0.77–2.18) 1.94 (1.33–2.82) 1.56 (1.29–1.89) 1

18.5–24.9 1 1 1 

25.0–29.9 0.86 (0.65–1.13) 0.95 (0.78–1.17) 0.92 (0.83–1.02) 

30.0–34.9 1.12 (0.77–1.64) 1.26 (0.97–1.63) 1.07 (0.94–1.22) 

35.0 and over 1.88 (1.27–2.79) 1.94 (1.32–2.87) 1.21 (0.97–1.51) 

In the frst 5 years after baseline: 

Under 18.5 1.48 (0.86–2.55) 1.76 (1.14–2.72) 1.54 (1.21–1.98) 1

18.5–24.9 1 1 1 

25.0–29.9 0.85 (0.61–1.17) 0.90 (0.73–1.11) 0.95 (0.85–1.07) 

30.0–34.9 1.25 (0.82–1.92) 1.25 (0.94–1.67) 1.11 (0.95–1.29) 

35.0 and over 2.18 (1.36–3.48) 2.02 (1.38–2.97) 1.15 (0.91–1.46) 

1

Reference category. 

NOTE: Body mass index is calculated as weight in kilograms (kg) divided by height in meters squared (m2

). 

SOURCE: NCHS, National Health and Nutrition Examination Survey, 1971–1994. 

To examine whether the increased relative risks at lower BMI levels might be 

related to possible weight loss associated with illness and increased mortality, 

which could have decreased the relative risks associated with overweight and 

obesity, the analyses excluding the first 3 or 5 years of deaths were repeated; little 

change in the relative risk estimates was seen (Table C). 

Health Status Analyses 

Self-reported health 

The association between self-reported 

health status and mortality was 

investigated using similar proportional 

hazards models and controlling for sex, 

BMI category, smoking, race–ethnicity 

group, and alcohol consumption. The 

self-reported health variable with 

five levels was a significant predictor 

of mortality in each survey and in 

the combined data set, as shown in 

Table D. Relative to the category of 

excellent or very good health, a selfreport of good, fair, or poor health was 

also a significant predictor of mortality, 

as shown in Table E. These results 

suggest that self-reported health is a 

reasonable indicator of overall health. 

For the combined sample, two 

categories of self-reported health 

status (excellent or very good, and 

good, fair, or poor) were stratified. 

Additionally, analyses for never 

smokers, stratified by health status, 

were repeated. After excluding the 

first 3 years of deaths, these analyses 

were repeated for never smokers 

stratified by health status. Thus, six 

sets of relative risks were calculated 

for each age group: excellent or very 

good health; good, fair, or poor health; 

never smokers with excellent or very 

good health; never smokers with good, 

fair, or poor health; never smokers 

with excellent or very good health, 

excluding the first 3 years of deaths; 

and never smokers with good, fair, or 

poor health, excluding the first 3 years 

of deaths. 

The estimates of relative risk from 

these analyses are shown in Table F 

for the categories of underweight 

(BMI less than 18.5), overweight 

(BMI 25–29.9), grade 1 obesity (BMI 

30–34.9), and grades 2 and 3 obesity 

(BMI greater than or equal to 35). In 

the combined analyses, stratification 

by health status, limiting the sample to 

never smokers, and excluding the first 

3 years of deaths did not change the 

direction of the relative risk estimates 

for underweight or overweight. In all 

cases, the relative risk for underweight 

Series 3, Number 42 5 NATIONAL CENTER FOR HEALTH STATISTICS 
was greater than 1 and the relative risk Table D. Adjusted relative risk (95% confidence interval) of mortality 

for overweight was under 1. associated with self-reported health status, by age group and survey: 

National Health and Nutrition Examination Survey, 1971–1994 For underweight, the relative risks did 

not tend to be closer to 1 after these 

exclusions. For example, for those aged 

70 and over who never smoked and 

were in excellent or very good health 

at baseline, after exclusion of the first 

3 years of deaths, the relative risk for 

underweight was 2.20 compared with 

1.69 for the full sample. 

For overweight, the relative risk for 

those aged 70 and over was 0.91 in 

the full sample. Depending on the 

exact exclusions or stratifications, the 

relative risk for overweight ranged from 

0.89 to 0.99. For those under age 70, 

the relative risks for overweight varied 

from 0.40 to 0.91. For never smokers 

aged 25–69 in excellent or very good 

health at baseline, after excluding the 

first 3 years of deaths, the relative risk 

for overweight was 0.45. 

These exclusions sometimes changed 

the direction of the relative risks for 

obesity categories from above 1 to 

below 1. For grade 1 obesity, the 

relative risks for those aged 70 and 

over ranged from 1.00 (for those in 

good, fair, or poor health at baseline) 

to 1.18 (for never smokers in good, 

fair, or poor health at baseline after 

excluding the first 3 years of deaths). 

For grade 1 obesity for younger never 

smokers, regardless of baseline health 

status and regardless of excluding the 

first 3 years of deaths, the relative risks 

were always below 1. 

Physician-evaluated health 

status 

The association between physicianevaluated health status and mortality 

in NHANES III was also investigated. 

The physician-evaluated health 

variable was a significant predictor of 

mortality in NHANES III (Table G). 

Relative to the excellent or very good 

category, a physician evaluation of 

health as good, fair, or poor was 

associated with increased mortality in 

NHANES III (Table H). When selfreported health status and physicianreported health status were both 

included in the models, both were 

Survey and health status 25–59 years 60–69 years 70 years and over 

NHANES I 

Excellent1 1 1 1 

Very good 1.44 (0.94–2.23) 1.03 (0.65–1.62) 1.04 (0.76–1.42) 

Good 1.46 (0.90–2.38) 1.44 (0.94–2.21) 1.24 (0.93–1.66) 

Fair 2.52 (1.60–3.98) 1.70 (1.13–2.54) 1.61 (1.21–2.15) 

Poor 3.77 (2.06–6.87) 2.94 (1.71–5.07) 1.56 (1.09–2.24) 

NHANES II 

Excellent1 1 1 1 

Very good 2.69 (1.43–5.06) 1.10 (0.64–1.87) 1.08 (0.87–1.34) 

Good 2.53 (1.36–4.71) 1.44 (0.92–2.24) 1.39 (1.13–1.72) 

Fair 3.18 (1.59–6.38) 2.34 (1.40–3.91) 1.76 (1.44–2.16) 

Poor 5.72 (2.77–11.8) 3.79 (2.30–6.24) 2.38 (1.94–2.91) 

NHANES III 

Excellent1 1 1 1 

Very good 1.01 (0.51–2.01) 0.91 (0.47–1.76) 1.07 (0.86–1.35) 

Good 1.60 (0.90–2.85) 1.61 (0.84–3.09) 1.30 (1.09–1.55) 

Fair 4.16 (2.01–8.61) 3.14 (1.60–6.18) 1.70 (1.37–2.12) 

Poor 4.25 (1.95–9.26) 6.17 (2.80–13.6) 2.58 (1.90–3.51) 

NHANES I, II, and III combined 

Excellent1 1 1 1 

Very good 1.44 (1.00–2.07) 0.99 (0.72–1.36) 1.07 (0.93–1.25) 

Good 1.75 (1.25–2.46) 1.47 (1.10–1.98) 1.31 (1.16–1.49) 

Fair 3.49 (2.28–5.32) 2.34 (1.72–3.19) 1.69 (1.46–1.95) 

Poor 4.23 (2.75–6.51) 4.00 (2.82–5.67) 2.29 (1.90–2.77) 

1

Reference category. 

NOTES: NHANES is National Health and Nutrition Examination Survey. Relative risks are adjusted for 

body mass index category, sex, smoking status, race–ethnicity group, and alcohol consumption. 

SOURCE: NCHS, NHANES, 1971–1994. 

Table E. Adjusted relative risk (95% confidence interval) of mortality for 

self-reported good, fair, or poor health relative to self-reported excellent 

or very good health, by age group and survey: National Health and 

Nutrition Examination Survey, 1971–1994 

Survey and health status 25–59 years 60–69 years 70 years and over 

NHANES I 

Excellent or very good1

Good, fair, or poor 

1 

1.52 (1.13–2.05) 

1 

1.62 (1.23–2.13) 

1 

1.36 (1.15–1.60) 

NHANES II 

Excellent or very good1

Good, fair, or poor 

1 

1.61 (1.11–2.34) 

1 

1.87 (1.48–2.38) 

1 

1.58 (1.37–1.82) 

NHANES III 

Excellent or very good1

Good, fair, or poor 

1 

2.27 (1.50–3.42) 

1 

2.53 (1.56–4.12) 

1 

1.48 (1.28–1.70) 

NHANES I, II, and III combined 

Excellent or very good1

Good, fair, or poor 

1 

1.85 (1.47–2.34) 

1 

1.98 (1.61–2.42) 

1 

1.47 (1.34–1.61) 

1

Reference category. 

NOTES: NHANES is National Health and Nutrition Examination Survey. Relative risks are adjusted for 

body mass index category, sex, smoking status, race–ethnicity group, and alcohol consumption. 

SOURCE: NCHS, NHANES, 1971–1994. 

NATIONAL CENTER FOR HEALTH STATISTICS 6 Series 3, Number 42 
Table F. Adjusted relative risk (95% confidence interval) of mortality, by age group, body mass index category, 

and selected exclusionary criteria: National Health and Nutrition Examination Survey, 1971–1994 

Body mass index under 18.5 Body mass index 25–29.9 Body mass index 30–34.9 Body mass index 35 and over 

Subgroup 

Under 

70 years 

70 years and 

over 

Under 

70 years 

70 years and 

over 

Under 

70 years 

70 years and 

over 

Under 

70 years 

70 years and 

over 

All 1.88 1.69 0.90 0.91 1.16 1.03 1.75 1.17 

(1.43–2.45) (1.38–2.07) (0.78–1.03) (0.83–1.01) (0.92–1.44) (0.91–1.17) (1.35–2.26) (0.94–1.47) 

Excellent or very good health 1.33 1.73 0.91 0.90 1.01 1.02 1.79 1.11 

(0.50–3.56) (1.10–2.70) (0.69–1.20) (0.75–1.09) (0.65–1.58) (0.82–1.28) (1.05–3.04) (0.67–1.84) 

Good, fair, or poor health 1.74 1.65 0.85 0.91 1.05 1.00 1.36 1.04 

(1.25–2.41) (1.29–2.11) (0.72–1.00) (0.80–1.02) (0.80–1.36) (0.84–1.19) (0.99–1.86) (0.81–1.33) 

Excellent or very good health, 3.36 2.00 0.40 0.97 0.53 1.14 1.67 0.63 

never smoked (0.75–15.1) (1.22–3.28) (0.21–0.76) (0.76–1.24) (0.26–1.11) (0.84–1.53) (0.74–3.78) (0.32–1.28) 

Good, fair, or poor health, 1.45 1.23 0.77 0.89 0.92 1.15 1.21 0.98 

never smoked (0.67–3.14) (0.82–1.85) (0.50–1.20) (0.76–1.04) (0.60–1.39) (0.94–1.41) (0.77–1.91) (0.72–1.33) 

Excellent or very good health, 

never smoked, frst 3 years 2.20 0.45 0.99 0.50 1.11 1.87 0.75 

of deaths excluded – (1.22–3.94) (0.22–0.90) (0.76–1.29) (0.21–1.16) (0.83–1.49) (0.78–4.44) (0.38–1.50) 

Good, fair, or poor health, 

never smoked, frst 3 years 1.47 1.21 0.76 0.89 0.89 1.18 1.37 0.90 

of deaths excluded (0.60–3.59) (0.80–1.83) (0.45–1.28) (0.75–1.06) (0.56–1.42) (0.94–1.49) (0.84–2.24) (0.65–1.22) 

– Quantity zero. 

NOTES: Relative risks are adjusted for sex, smoking status, race–ethnicity group, and alcohol consumption. Body mass index is calculated as weight in kilograms 

(kg) divided by height in meters squared (m2

). Reference category is body mass index 18.5–24.9. 

SOURCE: NCHS, National Health and Nutrition Examination Survey, 1971–1994. 

Table G. Adjusted relative risk (95% confidence interval) of mortality associated with five categories of 

physician-evaluated health status, by age group and model: National Health and Nutrition Examination Survey, 

1988–1994 

Model and health status 25–59 years 60–69 years 70 years and over 

Model 1 (sex, smoking, body mass index, 

alcohol consumption, and race–ethnicity group) 

Excellent1 1 1 1 

Very good 0.89 (0.51–1.54) 1.36 (0.74–2.52) 1.18 (0.92–1.51) 

Good 1.42 (0.92–2.21) 1.63 (0.89–2.99) 1.62 (1.30–2.02) 

Fair 6.39 (3.53–11.6) 3.74 (1.98–7.08) 2.57 (2.02–3.26) 

Poor 4.96 (1.60–15.4) 11.7 (3.98–34.2) 3.93 (3.15–4.92) 

Model 2 (Model 1 plus self-reported health status) 

Excellent1 1 1 1 

Very good 0.85 (0.49–1.46) 1.37 (0.75–2.50) 1.17 (0.91–1.49) 

Good 1.28 (0.85–1.91) 1.38 (0.78–2.42) 1.54 (1.22–1.95) 

Fair 4.56 (2.53–8.21) 2.56 (1.38–4.76) 2.30 (1.80–2.94) 

Poor 3.84 (1.34–11.0) 6.08 (2.12–17.5) 3.32 (2.65–4.18) 

1

Reference category. 

SOURCE: NCHS, National Health and Nutrition Examination Survey, 1988–1994. 

significant predictors of mortality. Of respondents who 

reported their health status as excellent or very good, 71.6% 

were also considered by the physician to have excellent or 

very good health. Of respondents who reported their health 

status as good, fair, or poor, 49.1% were also considered by 

the physician to have good, fair, or poor health. Of 

respondents who reported their health as excellent or very 

good, 90.5% reported no history of any of the following 

conditions: cancer (other than skin cancer), congestive heart 

failure, stroke, heart attack, emphysema, or diabetes. Of 

those who reported their health as good, fair, or poor, 73.5% 

also reported none of those conditions. The corresponding 

values for physician-evaluated health were 89.0% of those 

judged to be in excellent or very good health and 67.1% of 

those judged to be in good, fair, or poor health. 

For NHANES III, in which data were available on physicianevaluated health status, the analyses stratified by physicianevaluated health status at baseline were repeated, with 

results shown in Table J. These analyses use data from only 

Series 3, Number 42 7 NATIONAL CENTER FOR HEALTH STATISTICS 
 

Table H. Adjusted relative risk (95% confidence interval) of mortality for two categories of physician-evaluated 

health status, by age group and model: National Health and Nutrition Examination Survey, 1988–1994 

Model and health status 25–59 years 60–69 years 70 years and over 

Model 1 (sex, smoking, body mass index, 

race–ethnicity group, and alcohol consumption) 

Excellent or very good health1

Good, fair, or poor health

1 

2.13 (1.47–3.09) 

1 

1.88 (1.14–3.11) 

1 

1.81 (1.60–2.06) 

Model 2 (Model 1 plus self-reported health status) 

Excellent or very good health1

Good, fair, or poor health

1 

1.93 (1.37–2.72) 

1 

1.62 (0.99–2.66) 

1 

1.72 (1.50-1.97) 

1

Reference category. 

SOURCE: NCHS, National Health and Nutrition Examination Survey, 1988–1994. 

Table J. Adjusted relative risk (95% confidence interval) of mortality before and after stratifying by physicianevaluated health status and selected exclusionary criteria, by age group and body mass index category: 

National Health and Nutrition Examination Survey, 1988–1994 

Body mass index under 18.5 Body mass index 25–29.9 Body mass index 30–34.9 Body mass index 35 and over 

Subgroup 

Under 70 

years 

70 years and 

over 

Under 70 

years 

70 years and 

over 

Under 70 

years 

70 years and 

over 

Under 70 

years 

70 years and 

over 

All 2.18 1.67 0.92 0.89 1.10 0.91 1.65 0.98 

(1.19–4.00) (1.21–2.30) (0.68–1.24) (0.74–1.06) (0.70–1.73) (0.74–1.11) (1.02–2.68) (0.66–1.46) 

Excellent or very good health 0.89 1.61 1.04 0.94 1.23 0.77 1.39 0.44 

(0.16–5.00) (0.91–2.87) (0.60–1.81) (0.66–1.34) (0.64–2.37) (0.51–1.15) (0.59–3.29) (0.11–1.69) 

Good, fair, or poor health 2.41 1.50 0.77 0.86 0.74 0.85 1.15 0.85 

(1.24–4.69) (0.99–2.27) (0.58–1.04) (0.74–0.99) (0.40–1.36) (0.66–1.08) (0.73–1.84) (0.57–1.28) 

Excellent or very good health, 1.30 0.49 0.97 0.54 1.12 1.11 0.35 

never smoked – (0.68–2.51) (0.16–1.47) (0.62–1.49) (0.19–1.56) (0.61–2.07) (0.32–3.91) (0.08–1.51) 

Good, fair, or poor health; 9.61 1.22 0.94 0.93 0.54 0.98 1.24 0.71 

never smoked (1.98–46.7) (0.70–2.10) (0.32–2.83) (0.70–1.24) (0.19–1.53) (0.70–1.36) (0.56–2.74) (0.44–1.16) 

Excellent or very good health, 

never smoked, frst 3 years of 1.38 0.58 0.97 0.38 1.27 1.48 0.32 

deaths excluded – (0.69–2.75) (0.15–2.19) (0.59–1.58) (0.15–0.94) (0.68–2.39) (0.38–5.70) (0.06–1.72) 

Good, fair, or poor health; 

never smoked; frst 3 years of 2.00 1.26 0.58 0.92 0.50 1.04 1.07 0.65 

deaths excluded (0.20–19.7) (0.68–2.31) (0.20–1.70) (0.66–1.28) (0.16–1.61) (0.68–1.58) (0.44–2.65) (0.41–1.03) 

Excellent or very good health, 

never smoked, less than 2.5 kg 3.68 0.88 0.92 1.12 1.05 1.55 0.19 

reported net weight loss in 10 years – (1.77–7.65) (0.37–2.13) (0.59–1.44) (0.45–2.80) (0.67–1.63) (0.49–4.86) (0.02–1.63) 

Good, fair, or poor health; 

never smoked; less than 2.5 kg 1.45 1.84 0.91 0.86 1.26 0.93 1.76 1.03 

reported net weight loss in 10 years (0.38–5.59) (0.88–3.84) (0.46–1.81) (0.68–1.10) (0.57–2.76) (0.60–1.43) (0.79–3.90) (0.68–1.57) 

– Quantity zero. 

NOTES: Relative risks are adjusted for sex, smoking status, race–ethnicity group, and alcohol consumption. Body mass index is calculated as weight in kilograms 

(kg) divided by height in meters squared (m2

). The reference category is body mass index 18.5–24.9. 

SOURCE: NCHS, National Health and Nutrition Examination Survey, 1988–1994. 

one survey, and the prevalence of underweight is quite low 

(2.2%); thus, for some subgroups of underweight persons 

under age 70, the relative risks could not be estimated 

very precisely. No deaths occurred among the 57 younger 

underweight nonsmokers with excellent or very good health, 

so the estimate of relative risk was 0. 

In the NHANES III analyses for older people, underweight was 

associated with higher risk and overweight with lower risk. 

For younger people, overweight was generally associated 

with lower risk, with a single exception. These results, 

based on physician-evaluated health status at baseline, did 

not suggest that the results were affected in any large or 

systematic way by residual confounding due to illness. Even 

when analyses were restricted to never smokers judged to be 

in excellent or very good health by the physician, and after 

eliminating the first 3 years of deaths, the relative risks were 

below 1 for overweight and greater than 1 for underweight. 

Additional exclusions of respondents who reported a net 

weight loss of 2.5 kg or more during the 10 years before 

baseline had little impact on relative risks. For the older 

NATIONAL CENTER FOR HEALTH STATISTICS 8 Series 3, Number 42 
Table K. Adjusted relative risk (95% confidence interval) of mortality after stratifying by self-reported health 

status and excluding respondents with involuntary weight loss in 6 months prior to baseline: National Health 

and Nutrition Examination Survey, 1976–1980 

Body mass index under 18.5 Body mass index 25–29.9 Body mass index 30–34.9 Body mass index 35 or over 

Subgroup 

Under 70 

years 

70 years and 

over 

Under 70 

years 

70 years and 

over 

Under 70 

years 

70 years and 

over 

Under 70 

years 

70 years and 

over 

All 1.17 1.50 0.77 0.86 0.84 1.11 1.30 0.98 

(0.71–1.94) (1.06–2.11) (0.62–0.96) (0.75–0.99) (0.61–1.17) (0.86–1.42) (0.97–1.74) (0.75–1.29) 

Excellent or very good health 2.98 0.69 0.83 0.80 1.48 2.03 0.60 

– (1.72–5.17) (0.43–1.10) (0.63–1.09) (0.41–1.57) (1.04–2.10) (1.08–3.82) (0.20–1.74) 

Good, fair, or poor health 1.49 1.16 0.81 0.86 0.80 0.99 1.04 1.03 

(0.90–2.45) (0.80–1.69) (0.64–1.03) (0.72–1.02) (0.57–1.12) (0.73–1.35) (0.70–1.57) (0.81–1.32) 

Excellent or very good health, 2.40 0.64 0.68 1.32 1.20 3.39 0.72 

never smoked – (1.02–5.63) (0.18–2.21) (0.43–1.07) (0.43–4.00) (0.64–2.24) (1.11–10.4) (0.25–2.05) 

Good, fair, or poor health, 2.10 1.17 0.52 0.90 0.78 1.03 1.00 1.19 

never smoked (0.70–6.29) (0.45–3.07) (0.28–0.96) (0.67–1.19) (0.40–1.51) (0.67–1.56) (0.47–2.10) (0.83–1.70) 

Excellent or very good health, 

never smoked, frst 3 years of 2.55 0.78 0.71 1.33 1.32 4.32 0.79 

deaths excluded – (1.12–5.84) (0.22–2.79) (0.45–1.13) (0.33–5.27) (0.69–2.52) (1.38–13.50) (0.27–2.29) 

Good, fair, or poor health; 

never smoked; frst 3 years of 2.34 1.22 0.58 0.90 0.77 0.91 1.17 1.16 

deaths excluded (0.61–8.93) (0.46–3.23) (0.30–1.13) (0.66–1.22) (0.33–1.77) (0.60–1.38) (0.52–2.64) (0.80–1.69) 

Excellent or very good health, 

never smoked, frst 3 years of 

deaths excluded, recent involuntary 2.98 0.85 0.70 1.41 1.36 4.08 0.80 

weight loss excluded – (1.37–6.45) (0.23–3.09) (0.44–1.11) (0.33–5.97) (0.70–2.67) (1.29–12.9) (0.28–2.26) 

Good, fair, or poor health; 

never smoked; frst 3 years of 

deaths excluded; recent involuntary 0.74 0.62 0.94 1.05 0.99 1.43 1.25 

weight loss excluded – (0.19–2.87) (0.29–1.34) (0.67–1.31) (0.44–2.52) (0.63–1.56) (0.58–3.55) (0.82–1.89) 

– Quantity zero. 

NOTES: Relative risks are adjusted for sex, smoking status, race–ethnicity group, and alcohol consumption. Body mass index is calculated as weight in kilograms 

(kg) divided by height in meters squared (m2

). The reference category is body mass index 18.5–24.9. 

SOURCE: NCHS, National Health and Nutrition Examination Survey, 1976–1980. 

group, underweight was still associated with a relative risk 

greater than 1, and for both age groups, overweight was still 

associated with a relative risk below 1. 

For NHANES II only, these analyses were repeated, 

stratifying by self-reported baseline health status (Table K). 

Respondents who reported involuntary weight loss in the 

6 months before baseline were excluded. In this survey, all 

four exclusionary criteria were used. Although the relatively 

small sample size in this single survey made it difficult to 

estimate relative risks precisely in the group under 70, the 

relative risks estimated after these exclusions did not suggest 

that residual confounding or illness-induced weight loss had 

caused any systematic bias in the relative risk estimates. 

For persons aged 70 and over who had never smoked, had 

excellent or very good health at baseline, did not report 

recent involuntary weight loss, and after excluding the 

first 3 years of deaths (i.e., after using all four exclusionary 

criteria), the relative risk was 2.98 for underweight, 0.70 for 

overweight, 1.36 for grade 1 obesity, and 0.80 for grades 

2 and 3 obesity. The corresponding values before any 

exclusions were 1.50 for underweight, 0.86 for overweight, 

1.11 for grade 1 obesity, and 0.98 for grades 2 and 3 obesity. 

The prevalence of underweight was low, and in the group 

under 70, death rates were also low. In the group of 67 

persons under 70 with a BMI less than 18.5 who reported 

excellent or very good health, no deaths occurred during 

follow-up, yielding an estimated relative risk of 0. 

Effects of Age at Measurement 

The age group 70 and over included both persons whose 

weight and height had been measured at younger ages and 

had survived to age 70, and persons whose weight and height 

had been measured at age 70 or over. Additional analyses 

were performed to evaluate whether the relative risks for 

the age group 70 and over differed according to whether the 

original measurements of weight and height had been made 

under age 70 or at age 70 or over. The majority of deaths 

in the sample occurred in persons whose BMI had been 

measured before age 70. Data were stratified according to 

whether BMI was based on measurements made before age 

70 or at age 70 or over, with results by survey for the age 

group 70 and over as presented in Table M. 

Series 3, Number 42 9 NATIONAL CENTER FOR HEALTH STATISTICS 
 

Table M. Adjusted relative risk (95% confidence interval) of mortality for persons aged 70 and over, by survey, 

body mass index category, and age at measurement of weight and height: National Health and Nutrition 

Examination Survey, 1971–1994 

Body mass index

Survey and age at weight and 

height measurements Under 18.5 25–29.9 30–34.9 35 and over 

NHANES I 

All ages 2.01 (1.42–2.84) 0.99 (0.86–1.14) 1.20 (1.02–1.41) 1.92 (1.44–2.56) 

Measured under age 70 2.16 (1.40–3.34) 1.03 (0.85–1.25) 1.23 (0.98–1.53) 1.91 (1.33–2.74) 

Measured at age 70 or over 1.69 (1.05–2.69) 0.90 (0.75–1.08) 1.15 (0.89–1.49) 1.98 (1.14–3.43) 

NHANES II 

All ages 1.50 (1.06–2.11) 0.86 (0.75–0.99) 1.11 (0.86–1.42) 0.98 (0.75–1.29) 

Measured under age 70 1.53 (1.03–2.27) 0.88 (0.75–1.04) 1.16 (0.86–1.57) 1.03 (0.73–1.44) 

Measured at age 70 or over 1.30 (0.63–2.68) 0.81 (0.66–0.99) 0.95 (0.67–1.36) 0.92 (0.56–1.49) 

NHANES III 

All ages 1.67 (1.21–2.30) 0.89 (0.74–1.06) 0.91 (0.74–1.11) 0.98 (0.66–1.46) 

Measured under age 70 2.07 (0.97–4.41) 0.70 (0.44–1.12) 0.67 (0.42–1.09) 0.84 (0.40–1.77) 

Measured at age 70 or over 1.56 (1.14–2.14) 0.94 (0.79–1.12) 1.01 (0.80–1.27) 1.04 (0.68–1.59) 

NOTES: NHANES is National Health and Nutrition Examination Survey. Relative risks are adjusted for sex, smoking status, race–ethnicity group, and alcohol 

consumption. Body mass index is calculated as weight in kilograms (kg) divided by height in meters squared (m2

). The reference category is body mass index 

18.5–24.9. 

SOURCE: NCHS, NHANES, 1971–1994. 

Table N. Percentage of sample and percentage of deaths remaining before and after selected exclusionary 

criteria were applied, by age group and survey: National Health and Nutrition Examination Survey, 1971–1994 

NHANES I, II, and III combined NHANES II NHANES III 

Under 70 years Under 70 years Under 70 years 

Subgroup 70 years and over 70 years and over 70 years and over 

Sample 

All 100.0 100.0 100.0 100.0 100.0 100.0 

Excellent or very good health 51.9 36.7 49.6 35.0 49.7 37.9 

Excellent or very good health, never smoked 28.5 19.7 30.4 19.5 27.5 20.4 

Excellent or very good health, never smoked, 

frst 3 years of deaths excluded 28.2 19.1 30.1 19.3 27.2 19.4 

Excellent or very good health, never smoked, 

frst 3 years of deaths excluded, weight stable – – 26.8 17.6 23.4 15.6 

Deaths 

All 100.0 100.0 100.0 100.0 100.0 100.0 

Excellent or very good health 28.6 26.7 29.2 25.4 24.6 26.2 

Excellent or very good health, never smoked 20.7 15.4 21.8 15.9 18.1 14.9 

Excellent or very good health, never smoked, 

frst 3 years of deaths excluded 18.1 13.2 19.7 14.9 14.1 11.9 

Excellent or very good health, never smoked, 

frst 3 years of deaths excluded, weight stable – – 17.4 13.9 10.9 8.2 

– Quantity zero. 

NOTE: NHANES is National Health and Nutrition Examination Survey. 

SOURCE: NCHS, NHANES, 1971–1994. 

Proportions Excluded 

The proportion of the total sample remaining after sequential 

exclusions is shown in Table N. For the combined data set, 

after excluding smokers and those in poor health, about 28% 

of participants under age 70 and about 19% of participants 

aged 70 and over remained in the analytic sample. The 

additional exclusion of those who died in the first 3 years 

after baseline had only a slight effect. For NHANES II, when 

smokers; those in good, fair, or poor health; those who 

NATIONAL CENTER FOR HEALTH STATISTICS 10 Series 3, Number 42 
died within the first 3 years after baseline; and those who 

reported recent involuntary weight loss were all excluded 

from the analytic sample, about 27% of those under age 70

and 18% of those aged 70 and over remained in the analytic 

sample. Similar but slightly lower results were seen for 

NHANES III when similar criteria were applied. 

The weighted proportions of deaths in the analytic sample 

after exclusions are shown in the bottom half of Table M. 

After all exclusions in the combined data set, approximately 

18% of deaths in those under age 70 and 13% among those 

aged 70 and over remained in the analytic sample. After 

further exclusions for weight instability in NHANES II and 

NHANES III, the proportion of deaths remaining in the 

analytic sample fell even lower. For the older group in 

NHANES III, after all exclusions, only 8.2% of deaths remained 

in the analytic data set. 

Discussion 

The purpose of the analyses described above is to examine 

the impact of excluding study participants with potential 

confounding characteristics on the magnitude and direction 

of estimates of mortality relative risk in various BMI 

categories. Estimates of the population attributable fraction 

and the resulting absolute number of excess deaths use the 

point estimates of relative risk, regardless of their statistical 

significance. However, the variance of the relative risk 

estimates is incorporated into the overall variance of the 

estimated excess deaths. The discussion that follows refers 

to the point estimates and not to the statistical significance 

of the relative risks themselves. 

The object of these analyses is not to make statistical 

comparisons between subgroups, which are not independent 

of each other, nor to assess the statistical significance of 

the relative risk within a small subgroup. Rather, the object 

is to examine trends in the relative risks for indications 

that the estimates of excess deaths might be affected by 

systematic biases, such as those potentially due to illnessinduced weight loss or residual confounding by smoking or 

prevalent illness. These relative risks based on exclusions 

would not be appropriate to use to estimate excess deaths 

in the entire population. Relative risks that are adjusted for 

confounding factors need to be used in conjunction with the 

risks associated with those confounding factors. 

Relative Risk of Mortality Associated With 

Underweight 

The original analyses found that people who were 

underweight (BMI less than 18.5) had an elevated risk 

of mortality relative to persons of normal weight (BMI 

18.5–24.9). This observation persisted in virtually all analyses 

reported here. The prevalence of BMI less than 18.5 is quite 

low in the population, and in several categories of persons 

under age 70, in which the death rates are also lower, no 

deaths occurred. The analyses of NHANES I data for persons 

whose measured weight had changed by less than 2 kg over 

the preceding 10 years showed that underweight was still 

associated with an increased relative risk of mortality. The 

relative risk for underweight was also greater than 1 for 

people who had never smoked. When the analyses were 

further confined to people who had never smoked and 

reported having excellent or very good health at baseline, 

the relative risk for underweight was still greater than 1. 

Additional exclusions of early deaths and weight loss did not 

change the direction of the relative risk for underweight. For 

those aged 70 and over, the relative risk for underweight 

was always greater than 1. For younger ages, except for the 

small subgroups with no deaths, the risk was also greater 

than 1. When analyses of mortality in those aged 70 or over 

were restricted to participants whose weight and height 

had been measured before age 70, the relative risks in the 

underweight category increased, rather than decreased. 

These observations are consistent with findings in several 

other large samples. For example, in a prospective study 

with 10,858 participants, Thorogood et al. (34) found an 

increased mortality risk in those with BMI less than 18 and 

those with BMI 18 to less than 20 relative to BMI 20–22 after 

18 years of follow-up, even after excluding ever smokers and 

the first 5 years of deaths. These associations also persisted 

when the sample was restricted to participants who were 

under age 60 at baseline. Calle et al. (22) similarly found 

elevated mortality at low BMI levels in the large Cancer 

Prevention Study (CPS) II study relative to those with BMI 

23–25, even after excluding ever smokers and those with 

prevalent disease. 

Relative Risk of Mortality Associated With 

Overweight 

Analyses for the combined data set also showed a modestly 

reduced risk of mortality in the overweight category relative 

to the normal weight category. This reduction was observed 

in all surveys and age groups. A similar reduction was 

observed in analyses limited to weight-stable respondents 

in NHANES I, indicating that overweight that had persisted 

for at least 10 years was still associated with reduced risk. 

When data from the combined data set were stratified by 

self-reported health status, the relative risks for overweight 

continued to be less than 1 for both age groups. Additional 

exclusions of ever smokers and the first 3 years of deaths 

did not change the direction of the association; overweight 

was still associated with reduced mortality relative to the 

normal weight category. Similar results were observed in 

the NHANES III data when stratified by physician-evaluated 

health status. For respondents in excellent or very good 

health, the relative risk was slightly above 1 (1.04), but 

when analyses were additionally limited to never smokers, 

the relative risks dropped below 1. Additional exclusions of 

the first 3 years of deaths in NHANES III and of respondents 

reporting more than 2.5 kg of net weight loss in 5 years 

Series 3, Number 42 11 NATIONAL CENTER FOR HEALTH STATISTICS 
still resulted in relative risks less than 1 for the overweight 

category. Similar exclusions in NHANES II, including the 

exclusion of participants reporting recent involuntary 

weight loss, still resulted in relative risks less than 1 for the 

overweight category. This observation is also consistent with 

other studies. A meta-analysis of 26 cohorts found a relative 

risk of 0.97 for overweight relative to the normal weight 

category (19). 

Relative Risk of Mortality Associated With 

Obesity 

Slight but not systematic changes in relative risks, in both 

directions, were observed for both grade 1 and grades 2 

and 3 obesity, when data were stratified by health status, 

smoking, and weight change, and when early deaths were 

excluded. The relative risks sometimes increased and 

sometimes dropped below 1 for both obesity categories. 

Proportions Excluded 

The exclusionary approach resulted in the majority of the 

participants being excluded from the analytic sample. After 

exclusions on the basis of health status, smoking, early 

death, and weight stability, less than 30% of the original 

sample remained among participants under age 70, and 

less than 20% remained in those aged 70 and over. The 

proportion of deaths remaining was even lower. This high 

proportion of exclusions is comparable with that seen in 

other studies. In the Nurses’ Health Study, after limiting the 

sample to those without cardiovascular disease or cancer 

at baseline, exclusions on the basis of smoking and weight 

stability resulted in 88.8% of the deaths in the sample (4,195 

of 4,726 deaths) being excluded (24). The total proportion 

of excluded deaths in the cohort may have been higher, 

because participants with cancer or cardiovascular disease 

at baseline had previously been excluded. In the CPS II 

study, almost 82% of men and 63% of women in the analytic 

sample were excluded from further analysis (22). 

An examination of 15 epidemiologic cohorts demonstrated 

that results similar to those obtained by excluding smokers 

from the analytic sample were obtained by randomly 

deleting the same number of respondents (35). Those 

researchers concluded that, “The belief that smoking is 

responsible for the quadratic relation between BMI and 

mortality or that it explains the excess of mortality among 

the leanest groups is not supported by empirical observation 

or quantitative testing” (35). 

Conclusions 

These analyses of the effects of exclusions and stratification 

by health status for the combined data set do not suggest 

that the analyses on the full sample in the paper by Flegal 

et al. (3) were affected in any important or systematic way 

by residual confounding due to smoking, prevalent illness at 

baseline, or illness-induced weight loss. These analyses do 

not suggest that Flegal et al. (3) had overestimated the risks 

associated with underweight, or underestimated the risks 

associated with overweight or obesity. Even when analyses 

were restricted to a subset of healthy individuals who had 

never smoked and deaths occurring in the first part of the 

study were excluded, the relative risks were still elevated 

for underweight respondents and under 1 for overweight 

respondents, and the relative risks for obesity did not show 

an increase. Thus, these analyses do not suggest that biases 

due to illness-induced weight loss or residual confounding 

by smoking and prevalent illness explain the findings of 

Flegal et al. (3). 

References 

1. Hedley AA, Ogden CL, Johnson CL, Carroll MD, Curtin 

LR, Flegal KM. Prevalence of overweight and obesity 

among US children, adolescents, and adults, 

1999–2002. JAMA 291(23):2847–50. 2004. 

2. Flegal KM, Carroll MD, Ogden CL, Johnson CL. 

Prevalence and trends in obesity among US adults, 

1999–2000. JAMA 288(14):1723–7. 2002. 

3. Flegal KM, Graubard BI, Williamson DF, Gail MH. 

Excess deaths associated with underweight, 

overweight, and obesity. JAMA 293(15):1861–7. 2005. 

4. Gail MH, Brinton LA, Byar DP, Corle DK, Green SB, 

Schairer C, Mulvihill JJ. Projecting individualized 

probabilities of developing breast cancer for white 

females who are being examined annually. J Natl 

Cancer Inst 81(24):1879–86. 1989. 

5. Sturgeon SR, Schairer C, Gail M, McAdams M, Brinton 

LA, Hoover RN. Geographic variation in mortality from 

breast cancer among white women in the United 

States. J Natl Cancer Inst 87(24):1846–53. 1995. 

6. National Heart, Lung, and Blood Institute. Clinical 

guidelines on the identification, evaluation, and 

treatment of overweight and obesity in adults—The 

evidence report. Obes Res 6 Suppl 2:51S–209S. 1998. 

7. Obesity: Preventing and managing the global 

epidemic. Report of a WHO consultation. World Health 

Organ Tech Rep Ser 894:i–xii, 1–253. 2000. 

8. Korn EL, Graubard BI, Midthune D. Time-to-event 

analysis of longitudinal follow-up of a survey: Choice 

of the time-scale. Am J Epidemiol 145(1):72–80. 1997.

9. Thiebaut AC, Benichou J. Choice of time-scale in 

Cox’s model analysis of epidemiologic cohort data: A 

simulation study. Stat Med 23(24):3803–20. 2004.

10. Flegal KM, Graubard BI, Williamson DF. Methods 

of calculating deaths attributable to obesity. Am J 

Epidemiol 160(4):331–8. 2004. 

NATIONAL CENTER FOR HEALTH STATISTICS 12 Series 3, Number 42 
11. Flegal KM, Williamson DF, Pamuk ER, Rosenberg HM. 

Estimating deaths attributable to obesity in the United 

States. Am J Public Health 94(9):1486–9. 2004. 

12. Benichou J. A review of adjusted estimators of 

attributable risk. Stat Methods Med Res 10(3):

195–216. 2001. 

13. Rockhill B, Newman B, Weinberg C. Use and misuse of 

population attributable fractions. Am J Public Health 

88(1):15–9. 1998. 

14. Stampfer M. Weight loss and mortality: What does the 

evidence show? PLoS Med 2(6):e181. 2005. 

15. Willett WC, Dietz WH, Colditz GA. Guidelines for 

healthy weight. N Engl J Med 341(6):427–34. 1999. 

16. Klesges RC, Klesges LM, Meyers AW. Relationship of 

smoking status, energy balance, and body weight: 

Analysis of the Second National Health and Nutrition 

Examination Survey. J Consult Clin Psychol 59(6):

899–905. 1991. 

17. Wack JT, Rodin J. Smoking and its effects on body 

weight and the systems of caloric regulation. Am J Clin 

Nutr 35(2):366–80. 1982. 

18. Centers for Disease Control and Prevention. Annual 

smoking-attributable mortality, years of potential life 

lost, and economic costs—United States, 1995–1999. 

MMWR Morb Mortal Wkly Rep 51(14):300–3. 2002. 

19. McGee DL, Diverse Populations Collaboration. Body 

mass index and mortality: A meta-analysis based 

on person-level data from twenty-six observational 

studies. Ann Epidemiol 15(2):87–97. 2005. 

20. Sempos CT, Durazo-Arvizu R, McGee DL, Cooper RS, 

Prewitt TE. The influence of cigarette smoking on the 

association between body weight and mortality. The 

Framingham Heart Study revisited. Ann Epidemiol 

8(5):289–300. 1998. 

21. Ajani UA, Lotufo PA, Gaziano JM, Lee IM, Spelsberg A, 

Buring JE, et al. Body mass index and mortality among 

US male physicians. Ann Epidemiol 14(10):731–9. 

2004. 

22. Calle EE, Thun MJ, Petrelli JM, Rodriguez C, Heath CW 

Jr. Body-mass index and mortality in a prospective 

cohort of U.S. adults. N Engl J Med 341(15):1097–105. 

1999. 

23. Hu FB, Willett WC, Li T, Stampfer MJ, Colditz GA, 

Manson JE. Adiposity as compared with physical 

activity in predicting mortality among women. N Engl J 

Med 351(26):2694–703. 2004. 

24. Manson JE, Willett WC, Stampfer MJ, Colditz GA, 

Hunter DJ, Hankinson SE, et al. Body weight and 

mortality among women. N Engl J Med 333(11): 

677–85. 1995. 

25. Stevens J, Cai J, Pamuk ER, Williamson DF, Thun 

MJ, Wood JL. The effect of age on the association 

between body-mass index and mortality. N Engl J Med 

338(1):1–7. 1998. 

26. Baik I, Ascherio A, Rimm EB, Giovannucci E, 

Spiegelman D, Stampfer MJ, Willett WC. Adiposity 

and mortality in men. Am J Epidemiol 152(3):264–71. 

2000. 

27. Engel A, Murphy RS, Maurer K, Collins E. Plan and 

operation of the HANES I augmentation survey 

of adults 25–74 years, United States, 1974–1975. 

National Center for Health Statistics. Vital Health Stat 

1(14). 1978. 

28. McDowell A, Engel A, Massey JT, Maurer K. Plan and 

operation of the Second National Health and Nutrition 

Examination Survey, 1976–1980. National Center for 

Health Statistics. Vital Health Stat 1(15). 1981.

29. Plan and operation of the Third National Health and 

Nutrition Examination Survey, 1988–1994. National 

Center for Health Statistics. Vital Health Stat 1(32). 

1994. 

30. Miller HW. Plan and operation of the Health 

and Nutrition Examination Survey, United 

States—1971–1973. National Center for Health 

Statistics. Vital Health Stat 1(10a). 1973.

31. Cohen BB, Barbano HE, Cox CS, Feldman JJ, Finucane 

FF, Kleinman JC, Madans JH. Plan and operation of the 

NHANES I Epidemiologic Followup Study, 1982–1984. 

National Center for Health Statistics. Vital Health Stat 

1(22). 1987. 

32. Cox CS, Mussolino ME, Rothwell ST, Lane MA, Golden 

CD, Madans JH, Feldman JJ. Plan and operation of 

the NHANES I Epidemiologic Followup Study, 1992. 

National Center for Health Statistics. Vital Health Stat 

1(35). 1997. 

33. Loria CM, Sempos CT, Vuong C. Plan and operation of 

the NHANES II Mortality Study, 1992. National Center 

for Health Statistics. Vital Health Stat 1(38). 1999.

34. Thorogood M, Appleby PN, Key TJ, Mann J. Relation 

between body mass index and mortality in an 

unusually slim cohort. J Epidemiol Community Health 

57(2):130–3. 2003. 

35. BMI in Diverse Populations Collaborative Group. Effect 

of smoking on the body mass index–mortality relation: 

Empirical evidence from 15 studies. Am J Epidemiol 

150(12):1297–308. 1999. 

Series 3, Number 42 13 NATIONAL CENTER FOR HEALTH STATISTICS 
Vital and Health Statistics 

Series Descriptions 

Active Series 

Series 1. Programs and Collection Procedures 

Reports describe the programs and data systems of the 

National Center for Health Statistics, and the data collection 

and survey methods used. Series 1 reports also include 

defnitions, survey design, estimation, and other material 

necessary for understanding and analyzing the data. 

Series 2. Data Evaluation and Methods Research 

Reports present new statistical methodology including 

experimental tests of new survey methods, studies of vital and 

health statistics collection methods, new analytical techniques, 

objective evaluations of reliability of collected data, and 

contributions to statistical theory. Reports also include 

comparison of U.S. methodology with those of other countries. 

Series 3. Analytical and Epidemiological Studies 

Reports present data analyses, epidemiological studies, and 

descriptive statistics based on national surveys and data 

systems. As of 2015, Series 3 includes reports that would 

have previously been published in Series 5, 10–15, and 20–23. 

Discontinued Series 

Series 4. Documents and Committee Reports 

Reports contain fndings of major committees concerned with 

vital and health statistics and documents. The last Series 4 

report was published in 2002; these are now included in 

Series 2 or another appropriate series. 

Series 5. International Vital and Health Statistics Reports 

Reports present analytical and descriptive comparisons of 

U.S. vital and health statistics with those of other countries. 

The last Series 5 report was published in 2003; these are now 

included in Series 3 or another appropriate series. 

Series 6. Cognition and Survey Measurement 

Reports use methods of cognitive science to design, evaluate, 

and test survey instruments. The last Series 6 report was 

published in 1999; these are now included in Series 2. 

Series 10. Data From the National Health Interview Survey 

Reports present statistics on illness; accidental injuries; 

disability; use of hospital, medical, dental, and other services; 

and other health-related topics. As of 2015, these are included 

in Series 3. 

Series 11. Data From the National Health Examination Survey, the 

National Health and Nutrition Examination Surveys, and 

the Hispanic Health and Nutrition Examination Survey 

Reports present 1) estimates of the medically defned 

prevalence of specifc diseases in the United States and the 

distribution of the population with respect to physical, 

physiological, and psychological characteristics and 2) 

analysis of relationships among the various measurements. 

As of 2015, these are included in Series 3. 

Series 12. Data From the Institutionalized Population Surveys 

The last Series 12 report was published in 1974; these reports 

were included in Series 13, and as of 2015 are in Series 3. 

Series 13. Data From the National Health Care Survey 

Reports present statistics on health resources and use of 

health care resources based on data collected from health 

care providers and provider records. As of 2015, these reports 

are included in Series 3. 

Series 14. Data on Health Resources: Manpower and Facilities 

The last Series 14 report was published in 1989; these reports 

were included in Series 13, and are now included in Series 3. 

Series 15. Data From Special Surveys 

Reports contain statistics on health and health-related topics 

from surveys that are not a part of the continuing data systems 

of the National Center for Health Statistics. The last Series 15 

report was published in 2002; these reports are now included 

in Series 3. 

Series 16. Compilations of Advance Data From Vital and Health 

Statistics 

The last Series 16 report was published in 1996. All reports 

are available online; compilations are no longer needed. 

Series 20. Data on Mortality 

Reports include analyses by cause of death and demographic 

variables, and geographic and trend analyses. The last Series 

20 report was published in 2007; these reports are now 

included in Series 3. 

Series 21. Data on Natality, Marriage, and Divorce 

Reports include analyses by health and demographic 

variables, and geographic and trend analyses. The last Series 

21 report was published in 2006; these reports are now 

included in Series 3. 

Series 22. Data From the National Mortality and Natality Surveys 

The last Series 22 report was published in 1973. Reports from 

sample surveys of vital records were included in Series 20 or 

21, and are now included in Series 3. 

Series 23. Data From the National Survey of Family Growth 

Reports contain statistics on factors that affect birth rates, 

factors affecting the formation and dissolution of families, and 

behavior related to the risk of HIV and other sexually 

transmitted diseases. The last Series 23 report was published 

in 2011; these reports are now included in Series 3. 

Series 24. Compilations of Data on Natality, Mortality, Marriage, and 

Divorce 

The last Series 24 report was published in 1996. All reports 

are available online; compilations are no longer needed. 

For answers to questions about this report or for a list of reports published 

in these series, contact: 

Information Dissemination Staff 

National Center for Health Statistics 

Centers for Disease Control and Prevention 

3311 Toledo Road, Room 4551, MS P08 

Hyattsville, MD 20782 

Tel: 1–800–CDC–INFO (1–800–232–4636) 

TTY: 1–888–232–6348 

Internet: https://www.cdc.gov/nchs 

Online request form: https://www.cdc.gov/info 

For e-mail updates on NCHS publication releases, subscribe 

online at: https://www.cdc.gov/nchs/govdelivery.htm. 
U.S. DEPARTMENT OF

HEALTH & HUMAN SERVICES

Centers for Disease Control and Prevention

National Center for Health Statistics

3311 Toledo Road, Room 4551, MS P08

Hyattsville, MD 20782–2064

OFFICIAL BUSINESS 

PENALTY FOR PRIVATE USE, $300

FIRST CLASS MAIL

POSTAGE & FEES PAID

CDC/NCHS

PERMIT NO. G-284

DHHS Publication No. (PHS) 2018–1426, Series 3, No. 42

CS290481

For more NCHS Series Reports, visit:

https://www.cdc.gov/nchs/products/series.htm