Number 32 n January 12, 2011

Asthma Prevalence, Health Care Use, and Mortality: 

United States, 2005–2009 by Lara J. Akinbami, M.D., Office of Analysis and Epidemiology, National Center for Health Statistics; 

Jeanne E. Moorman, M.S., National Center for Environmental Health; and Xiang Liu, M.Sc., 

Office of Analysis and Epidemiology, National Center for Health Statistics 

Abstract

Objectives—This report presents recent data on asthma prevalence and health

care use. Additional data on school and work absences and asthma management

practices are also presented. Where possible, differences are examined by age, sex,

race or ethnicity, geographic region, poverty status, and urbanicity.

Methods—Data from the National Health Interview Survey, the National

Ambulatory Medical Care Survey, the National Hospital Ambulatory Medical Care

Survey, the National Hospital Discharge Survey, and the National Vital Statistics

System were used to calculate national estimates. The most recent data available

from each system are presented, and 3-year annual averages are used to increase the

reliability of estimates for subgroups where necessary.

Results—In 2009, current asthma prevalence was 8.2% of the U.S. population

(24.6 million people); within population subgroups it was higher among females,

children, persons of non-Hispanic black and Puerto Rican race or ethnicity, persons

with family income below the poverty level, and those residing in the Northeast and

Midwest regions. In 2008, persons with asthma missed 10.5 million school days and

14.2 million work days due to their asthma. In 2007, there were 1.75 million

asthma-related emergency department visits and 456,000 asthma hospitalizations.

Asthma emergency visit and hospitalization rates were higher among females than

males, among children than adults, and among black than white persons. Despite the

high burden from adverse impacts, use of some asthma management strategies

based on clinical guidelines for the treatment of asthma remained below the targets

set by the Healthy People 2010 initiative.

Keywords: school and work absence • ambulatory care • emergency department

visits • hospitalizations

Introduction

Asthma is a chronic respiratory

disease characterized by episodes or

attacks of impaired breathing.

Symptoms are caused by inflammation

and narrowing of small airways and

may include shortness of breath,

coughing, wheezing, and chest pain.

Disease severity ranges from mild with

occasional symptoms to severe with

persistent symptoms that impact quality

of life. However, even people with mild

disease may suffer severe attacks.

Common attack triggers include airway

irritants (e.g., tobacco smoke and air

pollution), allergens, respiratory

infections, stress, and exercise (1).

Although little is understood about

preventing asthma from developing, the

means for controlling and preventing

symptoms are well established.

Treatment includes the use of

medication for short-term relief; daily

use of preventive medication to avert

attacks; monitoring of early symptoms;

avoiding factors that trigger attacks; and

removing risks (e.g., tobacco smoke or

mold) from the home, school, and work

environments. Nevertheless, morbidity,

direct health care costs, indirect costs

such as lost productivity, and mortality

due to asthma continue pose a high

burden in the United States. The present

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Centers for Disease Control and Prevention 

National Center for Health Statistics 
Page 2 National Health Statistics Reports n Number 32 n January 12, 2011

report presents estimates for asthma

prevalence in the United States, as well

as for asthma-related health care use and

mortality. Differences between groups

are presented where data are available.

Methods

Data sources

Estimates for asthma prevalence,

school and work absences, and asthma

control measures are based on data from

the National Health Interview Survey

(NHIS). NHIS serves as a principal

source of health information for the U.S.

civilian noninstitutionalized population.

Questions used to ascertain asthma

prevalence are contained in the core

questionnaire asked of one sample adult

in each family included in NHIS, and, if

children are present, one sample child in

the family for whom a responsible adult

responds. Periodically, supplements with

special content for asthma are included

in the survey. In 2008, an asthma

supplement ascertained aspects of

disease control and asthma-specific

absences from school and work

(questionnaires for 2008 and other years

can be viewed at: http://www.cdc.gov/

nchs/nhis/nhis_questionnaires.htm).

Definitions and question wording for

estimates used in this report are found

in the ‘‘Technical Notes’’ section.

Ambulatory visit numbers and rates

were estimated using data from the

National Ambulatory Medical Care

Survey (NAMCS) and the National

Hospital Ambulatory Medical Care

Survey (NHAMCS). Visits to private

physician offices were estimated using

NAMCS, which samples visits made in

the United States to offices of

nonfederally employed physicians. Visits

to private, nonhospital-based clinics,

community health centers, and health

maintenance organizations were

included. Telephone contacts and visits

made outside of physician offices were

excluded. Visits to outpatient

departments (OPDs) and emergency

departments (EDs) were estimated using

NHAMCS, which samples visits made

to these departments in nonfederal

short-stay hospitals (average stay fewer

than 30 days) and in general hospitals

(medical or surgical) and children’s

general hospitals. EDs that operate

fewer than 24 hours were included in

the OPD component.

Data for asthma hospitalization

numbers and rates were obtained from

the National Hospital Discharge Survey

(NHDS). NHDS is a national probability

survey that collects data from a sample

of inpatient records acquired from a

national sample of nonfederal short-stay

hospitals in the United States. Only

hospitals with an average length of stay

of fewer than 30 days for all patients,

and general hospitals and children’s

general hospitals were included in the

survey.

Asthma death data were obtained

from the National Vital Statistics System

(NVSS). NVSS includes data on births

and deaths based on U.S. standard

certificates. The mortality component

was used to report asthma death rates.

Statistical analyses

For all health care surveys used in

this analysis (NAMCS, NHAMCS, and

NHDS), International Classification of

Diseases, Ninth Revision (ICD–9–CM)

code 493 was used to identify asthma.

Asthma deaths were those with an

underlying cause of death classified to

the International Classification of

Diseases, Tenth Revision (ICD–10)

codes J45–J46.

To calculate national numbers and

percentages from NHIS, NAMCS,

NHAMCS, and NHDS, survey weights

were used to inflate survey counts to

national counts (2). All estimates and

standard errors were estimated using

SUDAAN software (3) to account for

the complex sampling design of these

surveys. Only reliable estimates—those

with a relative standard error less than

or equal to 30%—are presented in this

report. Total population numbers and

rates for the most recent single year are

presented, whereas for subgroups, 3-year

annual averages from NAMCS,

NHAMCS, NHDS, and NVSS are

presented to ensure stable estimates.

Differences between percentages were

evaluated using two-sided significance

tests at the 0.05 level. No adjustments

were made for multiple comparisons.

Terms such as ‘‘similar’’ and ‘‘no

difference’’ indicate that the estimates

being compared were not significantly

different. However, lack of comment

regarding the difference between any

two statistics does not necessarily

suggest that the difference was tested

and found to be not significant.

The prevalence rate estimates

shown in Figure 2 (except age-specific

estimates) were age-adjusted using the

direct method and the 2000 U.S.

standard population. However,

prevalence numbers, health care use

numbers and rates, and mortality

numbers and rates were not ageadjusted, to allow evaluation of crude

estimates of health care utilization and

mortality.

The denominators for the rates of

health care use and mortality per the

population with current asthma were

obtained from NHIS. These

denominators are the estimated annual

average number of persons within the

specified group with reported current

asthma during the period 2005–2007.

Relative standard errors for these rates

were calculated using both the standard

error of the numerator and the

denominator.

More information concerning data

sources and statistical analyses is

provided in the ‘‘Technical Notes’’

section.

Results

Asthma prevalence

continues to increase

(Figure 1 and Table 1)

In 2009, current asthma prevalence

was 8.2%, affecting 24.6 million people

in the United States (17.5 million adults

and 7.1 million children aged 0–17

years) (Table 1). Asthma attack

prevalence—the proportion of the

population with at least one attack in the

previous year—was 4.2%. That is, 12.8

million people (8.7 million adults and

4.0 million children aged 0–17), or 52%

of those with current asthma, had

attacks and were at risk for adverse

outcomes such as ED visits or

hospitalization. The most rapid growth

in asthma prevalence occurred from
1

3

5

7

9

National Health Statistics Reports n Number 32 n January 12, 2011 Page 3

0 

2 

4 

6 

8 

10 

1980 1984 1988 1992 1996 2000 2004 2008

Asthma period prevalence1 

(1980–1996) 

1997 NHIS redesign

 Current asthma prevalence1 

(2001–2009) 

Asthma attack prevalence2 

(1997–2009)

Percent 1 Statistically significant trend. 

2 Trend not statistically significant. 

NOTE: See "Technical Notes" for definition of each prevalence type. 

SOURCE: CDC/NCHS, National Health Interview Survey (NHIS). 

Year 2009 

Figure 1. Asthma period prevalence, asthma attack prevalence, and current asthma

prevalence for all ages: United States, 1980–2009

1980 to 1996, when asthma period capture more detailed aspects of asthma

prevalence grew from 3.5% to 5.5%, an prevalence, and estimates before and

annual percentage increase of 3.8%. In after the change cannot be directly

1997, survey measures changed to compared. The measure most

comparable to the pre-1997 asthma

period prevalence estimate is current

asthma prevalence, which had remained

stable (at 7.4%) since it first became

available in 2001 but recently began

increasing so that overall, the annual

percentage increase from 2001 to 2009

was 1.2%. Asthma attack prevalence

remained level between 3.9% and 4.3%

during 1997–2009.

Asthma prevalence differs

by demographic

characteristics (Figure 2,

Table 2, and Figure 3)

Significant differences in current

asthma prevalence exist between many

population subgroups. Figure 2

compares 2009 current asthma

prevalence between population

subgroups. Overall, females have higher

current asthma prevalence than males,

although among children aged 0–17,

boys have a higher prevalence (11.3%)

than girls (7.9%). Children have higher

current asthma prevalence than adults.

Compared with white persons,

Male 

Female 

0–17 years

18 years and over

White 

Black 

American Indian or Alaska Native 

Asian 

Non-Hispanic white

Non-Hispanic black

Total Hispanic

Puerto Rican

Mexican 

Below poverty

100%–<200% poverty

200% poverty and above

Metropolitan

Nonmetropolitan

Northeast 

Midwest 

South 

West 

Total current asthma prevalence: 8.2% 

7.0 

9.6 

7.8 

11.1 

8.8 

5.3 

8.2 

11.1 

6.3 

4.9 

11.6 

8.5 

7.3 

8.1 

8.7 

9.3 

8.8 

7.5 

7.7 

16.6 

7.7 

9.3 

0 2 4 6 8 10 12 14 16

Percent 

NOTE: Estimates (except age-group-specific estimates) are age-adjusted to the year 2000 U.S. standard population. 

SOURCE: CDC/NCHS, National Health Interview Survey. 

 18 

Figure 2. Prevalence of current asthma, by selected characteristics: United States, 2009
Page 4 National Health Statistics Reports n Number 32 n January 12, 2011

Age in years 

Percent 

SOURCE: CDC/NCHS, National Health Interview Survey. 

0 

2 

4 

6 

8 

10 

12 

14 

16 

50 3025201510 35 85807570656055504540

Male 

Female 

Figure 3. Prevalence of current asthma among males and females aged 1–85 years, by age: United States, annual average 2001–2009

prevalence is higher among black and

lower among Asian persons. Compared

with non-Hispanic white and nonHispanic black persons, current asthma

prevalence is higher among Puerto

Rican and lower among Mexican

persons. Those with family income

below the federal poverty level have

higher asthma prevalence than those

with incomes in the near poor (100% to

less than 200% of poverty) and not poor

(200% of poverty and above) categories.

The near poor also have higher

prevalence compared with the not poor.

There is no difference in prevalence

rates between residents of metropolitan

and nonmetropolitan areas, but when

examined by geographic region,

prevalence is higher in the Northeast

than in the West and South and in the

Midwest compared with the South.

Figure 3 shows sex differences in

more detail across lifespan. Boys have

higher prevalence than girls throughout

most of childhood. During early

adolescence, current asthma prevalence

declines among males, whereas in

females, current asthma prevalence rises

steadily through childhood so that

between ages 14 and 17 years,

prevalence rates are similar among boys

and girls. This pattern of change

continues to early adulthood so that

throughout most of adulthood, women

report higher current asthma prevalence

compared with men.

School and work absences

are common among persons

with symptomatic asthma

(Table 3)

In 2008, children aged 5–17 years

with at least one asthma attack in the

previous year were reported to miss 10.5

million school days in the past year.

Nearly 60% had at least one asthma

absence day in the past year, and 5.5%

were reported to have an activity

limitation due to asthma. An activity

limitation is defined as a long-term

reduction in a person’s capacity to

perform the usual kind or amount of

activities associated with his or her age

group as a result of a chronic condition.

Adults aged 18 and over who had at

least one asthma attack in the past 12

months and were currently employed

reported missing 14.2 million work

days, and nearly 34% missed at least

one work day due to asthma in the

previous year. Among those employed,

6% of adults with at least one asthma

attack in the previous year reported that

a breathing problem caused an activity

limitation. Missed work days were also

measured among adults with at least one

asthma attack in the past 12 months

who were not currently employed and

included missed days of work around

the house. Among those not currently

employed, 22 million days of

housework or other types of activities

were missed, and 27% of those with at

least one asthma attack in the past 12

months reported an activity limitation

caused by a breathing problem.

Health care use for asthma

is high, and disparities

remain in asthma health care

use and mortality (Table 4

and Figure 4)

In 2007, 13.9 million visits for

asthma were made to private physician

offices (7.2 million for adults and 6.7
Female 

vs. male 

Other 

vs. white 

Black 

vs. white 

<18 vs. 

≥18 years 

0 1 2 3 4 

Death 

Hospitalization 

Emergency department visit 

Total ambulatory visit 0.82 

0.96 

1.08 

1.29 

0.68 

0.73 

0.89 

0.79 

3.32 

0.98 

2.22 

1.93 

1.77 

1.52 

1.23 

0.14 

Rate ratio 

NOTE: A rate ratio of 1.0 (dashed line) indicates equal rates between the groups being compared. 


SOURCES: CDC/NCHS, National Ambulatory Medical Care Survey, National Hospital Ambulatory Medical Care Survey,
 

National Hospital Discharge Survey, Mortality component of the National Vital Statistics System, and National Health 


Interview Survey (population with current asthma).
 

National Health Statistics Reports n Number 32 n January 12, 2011 Page 5

Figure 4. Relative burden of asthma health care use and mortality, adjusted for current

asthma prevalence, by sex, race, and age group: United States, annual average 2005–2007

million for children aged 0–17 years)

and 1.4 million visits to hospital OPDs

(0.6 million for adults and 0.8 million

for children aged 0–17 years). The

National Heart, Lung, and Blood

Institute guidelines for the clinical

management of asthma recommend

periodic preventive ambulatory visits for

asthma monitoring, and a proportion of

visits in nonemergent ambulatory

settings may reflect appropriate disease

management. In contrast, visits to EDs

and hospital stays for asthma represent

adverse outcomes. There were 1.75 

million ED visits (1.11 million for adults

and 0.64 million for children aged 0–17)

and 456,000 asthma hospitalizations

(299,000 for adults and 157,000 for

children aged 0–17). There were 3,447

deaths due to asthma in 2007 (3,262 

among adults and 185 among children

aged 0–17).

To account for differing prevalence

rates between groups and to focus on

the population at risk for these

outcomes, health care use rates in

Table 4 were calculated per 100 persons

with current asthma. Because numbers

of asthma deaths are smaller, death rates

were calculated per 10,000 persons with

current asthma. Estimates by income are

not available, and less detail is available

on health care use and mortality by race

or ethnicity. Even after accounting for

prevalence differences between groups,

differences are seen in health care use

and mortality burdens between groups.

Health care use is highest among

children aged 0–4 (rates per 100 persons

with current asthma for total ambulatory

visits were 144.9, for ED visits 24.6,

and for hospitalizations 8.4). However,

deaths from asthma are rare among

children aged 0–17, with 174 deaths on

average per year from 2005–2007.

To illustrate differences between

groups, the rates in Table 4 were used to

calculate the rate ratios shown in

Figure 4. A rate ratio of 1.0 indicates

equal rates between the groups being

compared. The largest differences are

seen for race and age groups. The

black-to-white rate ratio was nearly 1.0

for total ambulatory visits but was

greater than 1.0 for ED visits,

hospitalizations, and deaths. The rate

ratios for children compared with adults

were above 1.0 for all types of health

care services but below 1.0 for death.

Despite the large asthma

burden and the existence of

effective disease control

strategies, some Healthy

People 2010 targets for

asthma management have

not been met (Table 5)

The cornerstone of clinical

guidelines for the management of

asthma is control of symptoms and

prevention of adverse outcomes (1).

Some important components of

guideline-recommended management

that are also objectives of the Healthy

People 2010 initiative (4) are shown in

Table 5. In 2008, about 96% of people

with current asthma reported that a

health professional taught them how to

use their inhaler, nearly meeting the

target of 98.8%. However, 34% reported

receiving an asthma management plan

with specific instructions on how to

change the amount or type of medicine

taken, when to call a doctor for advice,

and when to go to the ED, and 60%

reported that they were taught how to

recognize early signs and symptoms of

an asthma episode. Report of receiving

these asthma control strategies differed

among groups, with generally higher

rates among children than adults and

among non-Hispanic black persons than

non-Hispanic white and Mexican

persons.

Summary

Although increases in asthma

prevalence have slowed since the

mid-1990s, asthma prevalence remains

at historically high levels. Current

asthma prevalence differs between

groups, with higher rates among

females, children, non-Hispanic black

and Puerto Rican persons, those with

family income below the poverty level,

and those residing in the Northeast and

Midwest regions. Asthma can involve

costs related to health care use and

morbidity, including missed work and

school days. Even after accounting for

prevalence differences between groups,

health care use differs among groups.

Non-Hispanic black persons have

relatively low rates of ambulatory visits
Page 6	 National Health Statistics Reports n Number 32 n January 12, 2011

compared with their use of urgent health

care services, which may represent

underuse of or lower access to

preventive services. In contrast, although

children have higher health care use

than adults, they have much lower death

rates. However, because adverse asthma

outcomes are theoretically preventable,

lowering asthma death rates among

people of all ages remains a priority.

The large asthma burden and continued

adverse outcomes present an ongoing

public health challenge, including the

effort to enhance uptake of underutilized

management strategies to control

symptoms.

References

1.	 National Asthma Education and

Prevention Program. Expert Panel

Report 3: Guidelines for the

diagnosis and management of

asthma. NIH pub no 07–4051.

Bethesda, MD: National Heart, Lung,

and Blood Institute, National

Institutes of Health. 2007. Available

from: http://www.nhlbi.nih.gov/

guidelines/asthma/.

2.	 Botman SL, Moore TF, Moriarity

CL, Parsons VL. Design and

estimation for the National Health

Interview Survey, 1995–2004.

National Center for Health Statistics.

Vital Health Stat 2(130). 2000.

Available from: http://www.cdc.gov/

nchs/data/series/sr_02/sr02_130.pdf.

3.	 RTI International. SUDAAN

language manual, release 10.

Research Triangle Park, NC: RTI

International. 2008.

4.	 U.S. Department of Health and

Human Services. Tracking Healthy

People 2010. Washington, DC:

Government Printing Office. 2000.

5.	 Schenker N, Raghunathan TE, Chiu

PL, Makuc DM, Zhang G, Cohen AJ.

Multiple imputation of family income

and personal earnings in the National

Health Interview Survey: Methods

and examples. National Center for

Health Statistics. 2008. Available

from: http://www.cdc.gov/nchs/data/

nhis/tecdoc.pdf.

6.	 Klein RJ, Schoenborn CA. Age

adjustment using the 2000 projected

U.S. population. Healthy People

2010 statistical notes, no 20.

Hyattsville, MD: National Center for

Health Statistics. 2001.

7.	 Joinpoint regression program, version

3.4 [computer software]. Bethesda,

MD: National Cancer Institute,

National Institutes of Health. 2010.

Available from: http://srab.cancer.

gov/joinpoint/.

8.	 Xu JQ, Kochanek KD, Murphy SL,

Tejada-Vera B. Deaths: Final data for

2007. National vital statistics reports;

vol 58 no 19. Hyattsville, MD:

National Center for Health Statistics.

2010. Available from: http://

www.cdc.gov/nchs/data/nvsr/nvsr58/

nvsr58_19.pdf.
National Health Statistics Reports n Number 32 n January 12, 2011 Page 7

Table 1. Asthma period prevalence, current asthma prevalence, and asthma attack

prevalence, for all ages: United States, 1980–2009

Asthma Current Asthma

period asthma attack

Year prevalence prevalence prevalence

Percent (standard error)

1980............................... 3.1 (0.2) – – – – – –

1981............................... 3.2 (0.2) – – – – – –

1982............................... 3.5 (0.2) – – – – – –

1983............................... 3.8 (0.2) – – – – – –

1984............................... 3.6 (0.2) – – – – – –

1985............................... 3.7 (0.2) – – – – – –

1986............................... 4.1 (0.3) – – – – – –

1987............................... 4.0 (0.2) – – – – – –

1988............................... 4.1 (0.2) – – – – – –

1989............................... 4.8 (0.2) – – – – – –

1990............................... 4.2 (0.2) – – – – – –

1991............................... 4.7 (0.2) – – – – – –

1992............................... 4.9 (0.2) – – – – – –

1993............................... 5.1 (0.3) – – – – – –

1994............................... 5.6 (0.3) – – – – – –

1995............................... 5.7 (0.3) – – – – – –

1996............................... 5.5 (0.3) – – – – – –

1997............................... ––– ––– 4.1 (0.1)

1998............................... ––– ––– 3.9 (0.1)

1999............................... ––– ––– 3.9 (0.1)

2000............................... ––– ––– 4.0 (0.1)

2001............................... ––– 7.4 (0.1) 4.3 (0.1)

2002............................... ––– 7.2 (0.2) 4.3 (0.1)

2003............................... ––– 7.0 (0.2) 3.9 (0.1)

2004............................... ––– 7.1 (0.2) 4.1 (0.1)

2005............................... ––– 7.6 (0.2) 4.2 (0.1)

2006............................... ––– 7.8 (0.2) 4.2 (0.1)

2007............................... ––– 7.7 (0.2) 4.2 (0.1)

2008............................... ––– 7.8 (0.2) 4.3 (0.1)

2009............................... ––– 8.2 (0.2) 4.2 (0.1)

– – – Data not available.

NOTES: Data are shown in Figure 1. See ‘‘Technical Notes’’ for definition of each prevalence type.

SOURCE: CDC/NCHS, National Health Interview Survey.
Page 8 National Health Statistics Reports n Number 32 n January 12, 2011

Table 2. Current asthma prevalence, by selected characteristics: United States, 2009

Number (rounded

to nearest Percent1

Characteristic hundred) (standard error)

Total ............................... 24,566,700 8.2 (0.2)

Sex

Male............................... 10,325,400 7.0 (0.3)

Female ............................. 14,241,300 9.3 (0.3)

Age

0–17 years ........................... 7,111,100 9.6 (0.4)

18 years and over ...................... 17,455,600 7.7 (0.2)

Race/ethnicity

White .............................. 18,533,500 7.8 (0.2)

Black .............................. 4,273,400 11.1 (0.6)

American Indian or Alaska Native ............. 233,700 8.8 (2.4)

Asian .............................. 721,600 5.3 (0.7)

Non-Hispanic white...................... 15,957,300 8.2 (0.3)

Non-Hispanic black...................... 4,068,700 11.1 (0.6)

Total Hispanic2 ............ ............ 2,997,000 6.3 (0.4)

Mexican ........................... 1,458,300 4.9 (0.4)

Puerto Rican ........................ 707,200 16.6 (1.9)

Percent of poverty level

Below 100% .......................... 5,086,900 11.6 (0.6)

100%–less than 200%.................... 5,056,100 8.5 (0.4)

200% and above ....................... 14,423,700 7.3 (0.2)

Urbanicity

Metropolitan .......................... 20.283,000 8.1 (0.2)

Nonmetropolitan ....................... 4,283,700 8.7 (0.5)

Geographic region

Northeast............................ 4,863,900 9.3 (0.5)

Midwest............................. 6,384,500 8.8 (0.5)

South .............................. 8,027,100 7.5 (0.3)

West. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5,291,200 7.7 (0.4)

1Age-adjusted to the year 2000 U.S. standard population, except age-group-specific estimates. 2Includes all Hispanic ethnicities, including Mexican, Puerto Rican, and others not shown separately. 

NOTES: Data are shown in Figure 2. Numbers for subgroups may not sum to total due to rounding. Numbers for race and 

ethnicity groups will not sum to the total because not all race/ethnicity groups are shown separately in the table, but all are 

included in the total. 

SOURCE: CDC/NCHS, National Health Interview Survey. 
National Health Statistics Reports n Number 32 n January 12, 2011 Page 9

Table 3. School and work absences and percentage with activity limitation caused by asthma, among persons with at least one asthma

attack in the past year: United States, 2008

Percent with

Percent with activity limitation

Weighted Total days one or more caused by

population missed,1 in asthma absence asthma or

size, in millions days in past year1 breathing problem

Population millions (standard error) (standard error) (standard error)

Children 5–17 years .......................... 3.3 10.5 (1.3) 58.7 (3.6) 5.5 (1.2) 

Adults 18 years and over, currently employed .......... 4.9 14.2 (4.7) 33.5 (2.8) 6.2 (1.3) 

Adults 18 years and over, not currently employed........ 3.8 22.0 (5.9) 29.1 (3.1) 26.5 (2.7) 

1Records with missing responses for days of school (1% among children aged 5–17 years), work (0.4% among adults currently employed), or housework or other activity (25.1% among adults not

currently employed) missed due to asthma are excluded.

SOURCE: CDC/NCHS, National Health Interview Survey.

Table 4. Asthma health care use per 100 persons with current asthma, and asthma deaths per 10,000 persons with current asthma, by

selected characteristics: United States, annual average 2005–2007

Per 100 persons with asthma

Hospital Total Emergency Deaths per

Office outpatient ambulatory department 10,000 persons

Characteristic visits visits visits visits Hospitalizations with asthma

Number (standard error)

Total.................................... 54.8 (5.6) 5.6 (0.7) 60.4 (5.6) 7.5 (0.4) 1.4 (0.2) 1.6 (0.0)

Sex

Male ................................... 61.6 (7.3) 5.8 (0.8) 67.4 (7.3) 7.7 (0.5) 1.3 (0.2) 1.4 (0.1)

Female .................................. 50.0 (6.2) 5.5 (0.7) 55.5 (6.2) 7.4 (0.5) 1.4 (0.2) 1.8 (0.0)

Race

White ................................... 57.4 (6.3) 4.6 (0.6) 62.0 (6.3) 5.6 (0.4) 0.9 (0.1) 1.4 (0.0)

Black ................................... 49.4 (9.2) 11.5 (2.1) 60.9 (9.4) 18.6 (1.6) 2.0 (0.3) 2.7 (0.1)

Other ................................... 38.5 (9.5) 3.4 (0.8) 41.9 (9.5) 4.1 (0.8) 0.8 (0.2) 1.1 (0.1)

Ethnicity

Hispanic ................................. 72.1 (19.8) 11.1 (2.3) 83.2 (19.9) 10.7 (1.2) – – – 0.9 (0.1)

Non-Hispanic .............................. 52.4 (5.4) 4.8 (0.6) 57.2 (5.4) 7.1 (0.4) – – – 1.7 (0.1)

Age

Under 18 years ............................. 77.5 (10.3) 9.7 (1.7) 87.2 (10.4) 9.9 (0.9) 1.6 (0.3) 0.3 (0.0)

18 years and over ........................... 45.4 (5.4) 3.9 (0.5) 49.3 (5.4) 6.5 (0.4) 1.3 (0.2) 2.1 (0.1)

– – – Data on Hispanic ethnicity are not available for hospitalization.

SOURCES: CDC/NCHS, National Ambulatory Medical Care Survey, National Hospital Ambulatory Medical Care Survey, National Hospital Discharge Survey, mortality component of the National

Vital Statistics System, and National Health Interview Survey (population with current asthma).
Page 10 National Health Statistics Reports n Number 32 n January 12, 2011

Table 5. Percentage (standard error) with current asthma, or parents of children with current asthma, who reported receiving key asthma

education or management strategies from a health care professional, by selected characteristics: United States, 2008

Advised to

Taught how to change things

recognize early at home,

signs or symptoms school, or Taught how to

Taught how to use Given an asthma of an work to respond to an

Characteristic an inhaler management plan asthma episode improve asthma episode of asthma

Healthy People 2010 target ..................... 98.8 40.0 68.0 50.0 68.0

Percent (standard error)

Total.................................... 95.9 (0.5) 34.2 (1.2) 60.0 (1.3) 50.9 (1.3) 68.2 (1.2)

Sex

Male ................................... 96.0 (0.8) 35.4 (2.0) 61.1 (2.0) 48.7 (2.1) 67.8 (2.0)

Female .................................. 95.8 (0.7) 33.2 (1.6) 59.0 (1.6) 52.7 (1.6) 68.5 (1.5)

Race/ethnicity

Non-Hispanic white .......................... 96.0 (0.7) 32.5 (1.6) 57.0 (1.7) 50.6 (1.7) 67.3 (1.6)

Non-Hispanic black .......................... 94.3 (1.4) 44.0 (2.8) 69.2 (2.4) 52.4 (2.7) 72.6 (2.4)

Puerto Rican .............................. 93.0 (2.8) 37.3 (6.4) 69.8 (6.2) 57.2 (6.7) 68.3 (6.3)

Mexican ................................. 97.7 (1.3) 28.8 (3.5) 54.7 (4.3) 42.3 (4.4) 58.7 (4.4)

Age

Under 18 years ............................. 95.9 (0.9) 44.3 (2.3) 72.1 (2.0) 53.2 (2.5) 78.4 (1.9)

18 years and over ........................... 95.9 (0.6) 29.9 (1.4) 54.8 (1.6) 50.0 (1.5) 63.8 (1.5)

Percent of poverty level

Below 100%............................... 93.7 (1.6) 31.1 (2.6) 57.9 (2.9) 49.9 (2.9) 63.8 (2.8)

100%–less than 200% ........................ 94.5 (1.2) 33.6 (2.6) 58.7 (2.8) 52.5 (2.8) 65.2 (2.7)

200% and above ............................ 97.0 (0.6) 35.3 (1.6) 61.0 (1.8) 50.6 (2.2) 70.5 (1.7)

SOURCE: CDC/NCHS, National Health Interview Survey.
National Health Statistics Reports n Number 32 n January 12, 2011 Page 11

Technical Notes

Findings presented in this report

were based on data from the National

Health Interview Survey, the National

Ambulatory Medical Care Survey, the

National Hospital Ambulatory Medical

Care Survey, the National Hospital

Discharge Survey, and the mortality

component of the National Vital

Statistics System. Survey descriptions,

question wording for estimates,

descriptions of statistical analyses, and

definitions are provided below.

National Health Interview

Survey (NHIS)

Sample design

NHIS is a cross-sectional household

interview survey of the U.S. civilian

noninstitutionalized population. Data are

collected continuously throughout the

year in all 50 states and the District of

Columbia. NHIS uses a multistage,

clustered sample design to produce

national estimates for a variety of health

indicators (Table). Information on basic

health topics is collected for all

household members. Interviews are

conducted in the home by field staff

from the U.S. Census Bureau, using a

computer-assisted personal interviewing

system, with telephone interviewing

permitted for follow-up if necessary.

Starting in 2006, the sample design

oversampled Asian persons; during

2001–2005, only households with black

and Hispanic residents were

oversampled. From 2001 to 2009, the

final response rate for each survey

component (which takes into account

household nonresponse) ranged from

81.6% to 88.1% for the family

questionnaire, 72.3% to 81.3% for the

sample child, and 62.6% to 74.3% for

the sample adult. More information is

available at: http://www.cdc.gov/nchs/

nhis.htm.

Item nonresponse

From 2001 through 2009, item

nonresponse for each of the

demographic indicators shown in this

report was generally less than 1%, with

the exception of poverty status, which is

based on detailed family income

ascertained from the Family Core

component of the questionnaire. Because

the item nonresponse for the poverty

status variable was relatively high

(22%–31% from 1997 through 2007),

family income data were imputed for

families with missing values (5). The

denominators for asthma prevalence

exclude persons with unknown

information about asthma status (less

than 0.8% for all years 1997–2009).

National Ambulatory Medical

Care Survey (NAMCS)

Sample design

NAMCS is an annual probability

survey of nonfederal, office-based

physicians providing direct patient care

who practice in the 50 states or the

District of Columbia, excluding

radiologists, anesthesiologists, and

pathologists. NAMCS collects data from

a national sample of over 2,000

physicians each year who provide

information on nearly 30,000 visits.

Because persons with multiple visits

during the year may be sampled more

than once, estimates are for visits, not

persons. NAMCS uses a multistage

sample design and sampling weights

applied to each record to provide

nationally representative estimates.

Visits to private, nonhospital-based

clinics and health maintenance

organizations were within the scope of

the survey, but visits that occurred in

federally operated facilities and

hospital-based OPDs were not. A sample

of office-based physicians who reported

that they were in direct patient care was

taken from the master files of the

American Medical Association and the

American Osteopathic Association. The

sample design includes 112 geographic

primary sampling units. Within those

units, physicians were stratified by

specialty, and a sample of physicians

was selected. Physicians were randomly

assigned to 1 of 52 reporting weeks

throughout the year. Between 2005 and

2007, the overall unweighted physician

response rate ranged from 58.9% to

61.6%. More information is available at:

http://www.cdc.gov/nchs/ahcd.htm.

Item nonresponse

Item nonresponse rates in NAMCS

are generally low (5% or less). Sex was

imputed for 0.8%–1.6% of records with

missing values, and birth year for

1.9%–2.5%, in the survey years

2005–2007. During this period, race was

imputed for 20.8%–32.9% of visits and

ethnicity for 24.9%–31.0%. In contrast

to the imputation method used to impute

race and ethnicity in previous years

(random assignment of a value from a

patient record form with similar

characteristics based on physician

specialty, geographic region, and

three-digit ICD–9–CM code for primary

diagnosis), a hierarchical procedure was

used in 2006. Cases missing race (or

ethnicity) were initially assigned a

donor’s value after matching donor and

recipient by three-digit ICD–9–CM

codes for primary diagnosis and ZIP

Code of the patient making the sampled

visit. If no donor was found after

several matching rounds of increasing

geographic size (county, state, region),

traditional imputation procedures were

applied. If both race and ethnicity were

missing, both were imputed from the

same donor. Standard errors may be

underestimated because single

imputation was used.

National Hospital

Ambulatory Medical Care

Survey (NHAMCS)

Sample design

NHAMCS is a national probability

sample survey of in-person visits made

in the United States to EDs and OPDs

of nonfederal short-stay hospitals

(hospitals with an average stay of fewer

than 30 days) and those whose specialty

is general (medical or surgical) or

children’s general. EDs that operate 24

hours a day are considered within the

scope of the ED component; EDs that

operate fewer than 24 hours are

included in the OPD component of

NHAMCS. The hospital sampling frame

for 2006 consisted of hospitals listed in

the 1991 Verispan Hospital Database

(formerly known as the SMG Hospital

Database) updated using hospital data
Page 12 National Health Statistics Reports n Number 32 n January 12, 2011

Table. Definitions and questions for NHIS asthma prevalence, school and work absences, and asthma control measures

Estimate NHIS question Questionnaire

Asthma period prevalence............. 

Current asthma prevalence ............ 

Asthma attack prevalence............. 

Missed work day .................. 

Missed school day ................. 

Taught how to use an inhaler........... 

Given an asthma management plan ......

Taught how to recognize early signs or

symptoms of an asthma episode ........

Advised to change things at home, school, or

work to improve asthma ..............

Taught how to respond to an episode of

asthma ........................

Activity limitation caused by asthma/breathing

problem ........................

During the past 12 months, did anyone in the family

have asthma?

Has a doctor or other professional ever told you that

[you/your child] had asthma?

and

[Do you/does your child] still have asthma?

Has a doctor or other professional ever told you that

[you/your child] had asthma?

and

During the past 12 months, [have you/has your child]

had an episode of asthma or an asthma attack?

During the past 12 months, how many days were you

unable to work because of your asthma?

During the past 12 months, how many days of [daycare/

preschool/school/school or work] did your child miss

because of [his/her] asthma?

Has a health professional shown [you/your child] how to

use [your/your child’s] inhaler?

Has a doctor or other health professional ever given

[you/your child] an asthma action plan?

Has a doctor or other health professional ever taught

[you/your child] how to recognize early signs or

symptoms of an asthma episode?

Has a doctor or other health professional ever advised

you to change things in [your/your child’s] home, school,

or work to improve [your/your child’s] asthma?

Has a doctor or other health professional ever taught

[you/your child] how to respond to episodes of asthma?

This estimate is based on a series of questions on the

Family Core questionnaire about limitations in activities

of daily living, instrumental activities of daily living,

school, work, difficulty walking or remembering, and any

other activity limitations: Are [you/your child] limited in

any way because of physical, mental, or emotional

problems?

For persons with a limitation, a question is asked: What

conditions or health problems cause [you/your child]

limitations?

For adults: Lung or breathing problem?

For children: Asthma or a breathing problem?

1982–1996 NHIS Respiratory Conditions questionnaires

2001 forward, NHIS Sample Child and Sample Adult

Core questionnaires

1997 forward NHIS Sample Child and Sample Adult Core

questionnaires

2008 NHIS Sample Adult Asthma Module questionnaire

2008 NHIS Sample Child Asthma Module questionnaire

2008 NHIS Sample Adult and Sample Child Asthma

Module questionnaires

2008 NHIS Sample Adult and Sample Child Asthma

Module questionnaires

2008 NHIS Sample Adult and Sample Child Asthma

Module questionnaires

2008 NHIS Sample Adult and Sample Child Asthma

Module questionnaires

2008 NHIS Sample Adult and Sample Child Asthma

Module questionnaires

2008 NHIS Person File summary variables based on

multiple questions from the Family Core questionnaire.

See: ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/

Survey_Questionnaires/NHIS/2008/English/qfamily.pdf.

SOURCE: CDC/NCHS, National Health Interview Survey (NHIS).

from Verispan, L.L.C. (Yardley,

Pennsylvania). About 500 hospitals are

included in the sample, from which about

1,200 OPDs and 400 EDs are selected.

Because persons with multiple visits

during the year may be sampled more

than once, estimates are for visits, not

persons. NHAMCS uses a multistage

probability sample and sampling weights

applied to each record to produce

nationally representative estimates.

Between 2005 and 2007, the overall

unweighted hospital response rate ranged

from 89.4% to 90.7%. More information

is available at: http://www.cdc.gov/nchs/

ahcd.htm.

Item nonresponse

Item nonresponse rates in NHAMCS

are generally low (5% or less), with some

exceptions. Sex was imputed for 0.3%–

0.7% of records with missing values, and

birth year for 0.7%–1.9%, in the survey

years 2005–2007. During this period, race

was imputed for 9.8%–14.9% of visits

and ethnicity for 17.0%–24.9%. In

contrast to imputation methods used in

previous years for race and ethnicity

(random assignment of a value from a

patient record form with similar

characteristics based on physician

specialty, geographic region, and

three-digit ICD–9–CM code for primary

diagnosis), in 2006, cases missing race or

ethnicity were initially assigned a donor’s

value after matching donor and recipient

by three-digit ICD–9–CM codes for

primary diagnosis and ZIP Code of the

patient making the sampled visit; if no

donor was found after several matching

rounds, imputation procedures based on

geographic region, OPD volume by clinic

type, and three-digit ICD–9–CM codes

for primary diagnosis were applied. If
National Health Statistics Reports n Number 32 n January 12, 2011 Page 13

both race and ethnicity were missing,

both were imputed from the same donor.

Beginning in 2007, a new method was

used to impute race and ethnicity. Race

and ethnicity assignments were based,

where possible, on diagnosis and

patient’s locality (ZIP Code or state or

county of residence). A hot deck

approach (i.e., filling in missing values

on incomplete records using values from

similar but complete records of the same

data set) was employed, rather than the

previously used cold deck strategy (i.e.,

filling in missing values on incomplete

records using values from similar but

complete records of the data set from

the previous year), except in cases

where a matching record could not be

obtained from the current data. When

race or ethnicity data could not be

assigned using patient locality, the new

method attempted to impute within the

same facility wherever possible. Failing

that, imputation was based on diagnosis,

hospital, type of emergency service area,

immediacy, and, as a last resort, on a

randomly selected record.

National Hospital Discharge

Survey (NHDS)

Sample design

NHDS collects data from a sample

of inpatient records acquired from a

national sample of hospitals. Because

persons with multiple discharges during

the year may be sampled more than

once, estimates are for discharges, not

persons. Only hospitals with an average

length of stay of fewer than 30 days for

all patients, and general hospitals and

children’s general hospitals, are included

in the survey. Federal, military, and

Department of Veterans Affairs

hospitals, as well as hospital units of

institutions (e.g., prison hospitals), and

hospitals with fewer than six beds

staffed for patient use are excluded.

NHDS collects data from a sample of

approximately 270,000 inpatient records

acquired from a national sample of

about 500 hospitals. A three-stage

sampling design procedure is used to

produce national estimates of hospital

discharges. Weights are assigned to each

sample record. Between 2005 and 2007,

the overall unweighted hospital response

rate ranged from 88% to 93%. More

information is available at: http://

www.cdc.gov/nchs/about/major/hdasd/

nhds.htm.

Item nonresponse

Less than 1% of records failed to

include the sex, age, or date of birth of

the patient. If the hospital record did not

state either the age or sex of patient, the

characteristic was imputed by assigning

an age or sex value that maintained the

known distribution of these variables

according to the categories of the

first-listed diagnosis. In a very few cases

(less than 1% of the records), the age or

sex was edited because it was

inconsistent with the diagnosis. For the

period 2005–2007, data for race were

missing for 28%–30% of the discharges,

and no attempt was made to impute for

these missing values. Nonresponse for

ethnicity is generally higher than for

race; therefore, ethnicity was not

imputed and is not reported in this

analysis.

Mortality component of the

National Vital Statistics

System (NVSS)

Data are based on information from

all death certificates filed in the 50

states and the District of Columbia and

are processed by the Centers for Disease

Control and Prevention’s National

Center for Health Statistics (NCHS).

Mortality statistics are based on

information coded by the states and

provided to NCHS through the Vital

Statistics Cooperative Program, as well

as from copies of original certificates

received by NCHS from state

registration offices. More information is

available at: http://www.cdc.gov/nchs/

deaths.htm.

Age adjustment

Data for the percentages shown in

Figure 2 and Table 2 were age-adjusted

using the 2000 U.S. population provided

by the U.S. Census Bureau as the

standard population (6). Age adjustment

was used to allow comparison among

various population subgroups that have

different age composition. The following

age groups were used for age

adjustment: under 1 year, 1–4 years,

5–14 years, 15–25 years, 25–34 years,

35–44 years, 45–54 years, 55–64 years,

65–74 years, 75–84 years, and 85 years

and over.

Estimation of counts

The estimated counts of persons

affected by asthma (NHIS), number of

office visits for asthma to private

physician offices (NAMCS), visits to

hospital OPDs (NHAMCS) and EDs

(NHAMCS), and asthma hospitalizations

(NHDS) are calculated by weighting the

number of respondents or visits by the

survey weights. Age-adjusted estimates

of counts of numbers of persons

affected by asthma are not presented

because only the crude numbers are of

interest.

Tests of significance

Statistical tests performed to assess

the significance of differences in

estimates were two-tailed, with no

adjustments for multiple comparisons.

The test statistic used to determine

statistical significance of differences

between two percentages was

|Xa–Xb|

Z = 2 2 √Sa + Sb

where Xa and Xb are the two

percentages being compared, and Sa and

Sb are the standard errors of those

percentages. The critical value used for

two-sided tests at the 0.05 level of

significance was 1.96.

The significance of trends was

tested using Joinpoint software (7) to

determine whether an apparent change

over time was statistically significant,

taking into account the standard error

for each data point. The weighted least

squares regression models produce an

annual percentage rate change when a

log of the outcome is analyzed.

Relative standard error

Estimates with a relative standard

error (RSE) greater than 30% are not

reported. The RSE of an estimate is

calculated as:
Page 14 National Health Statistics Reports n Number 32 n January 12, 2011

RSE (percent) = (SEst/Est) * 100,

where SEst is the standard error of the

estimate and Est is the estimate.

Definition of terms

Age—Recorded for each person as

of his or her last birthday.

Hispanic or Latino origin—Includes

persons of Mexican, Puerto Rican,

Cuban, Central and South American, or

Spanish origin. Persons of Hispanic or

Latino origin may be of any race.

Poverty status—Based on family

income and family size, using the U.S.

Census Bureau’s poverty thresholds.

‘‘Poor’’ persons are defined as those

with family incomes below the poverty

threshold. Persons who are ‘‘near poor’’

have family incomes of 100% to less

than 200% of the poverty threshold, and

persons who are ‘‘not poor’’ have family

incomes that are 200% of the poverty

threshold or above.

Race and Hispanic origin—The

collection of race and Hispanic origin data

in NHIS, NAMCS, NHAMCS, and NHDS

conforms with the 1997 U.S. Office of

Management and Budget’s Revisions to the

Standards for the Classification of Federal

Data on Race and Ethnicity. The 1997

Standards specify five racial groups as the

minimum for data collection on race in

federal statistics: American Indian or

Alaska Native, Asian, Black or African

American, Native Hawaiian or Other

Pacific Islander, and White. The standards

also offer respondents the opportunity to

select more than one of the five groups.

Hispanic or Latino origin includes persons

of Mexican, Puerto Rican, Cuban, Central

and South American, and other or

unknown Latin American or Spanish

origin. Persons of Hispanic origin may be

of any race. The NVSS mortality

component conformed to the 1997

Standards in 21 states in 2005 and

increased to 27 states and the District of

Columbia in 2007. To provide uniformity

and comparability of NVSS mortality data

during the transition period, before all or

most of the data become available in the

new multiple-race format, the responses of

those for whom more than one race was

reported (multiple race) are bridged to a

single race (8).
Page 16 National Health Statistics Reports n Number 32 n January 12, 2011

Suggested citation

Akinbami LJ, Moorman JE, Liu X. Asthma

prevalence, health care use, and mortality:

United States, 2005–2009. National health

statistics reports; no 32. Hyattsville, MD:

National Center for Health Statistics. 2011.

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.

National Center for Health Statistics

Edward J. Sondik, Ph.D., Director 

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

for Science 

Office of Analysis and Epidemiology

Linda T. Bilheimer, Ph.D., Director

U.S. DEPARTMENT OF

HEALTH & HUMAN SERVICES

Centers for Disease Control and Prevention

National Center for Health Statistics

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Hyattsville, MD 20782

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