NCHS Data Brief ■ No. 41 ■ August 2010

u.s. department of health and human services

Centers for Disease Control and Preven

National Center for Health Statis

Population Aging and the Use of Office-based Physician 

Services

Donald C, M.s.; christine L.p.h., m.S.W.; and Sandra L

Key findings

•	 From 1998 to 2008, the 

proportion of physician officebased visits in the United 

States became increasingly 

concentrated on those aged 45 

and over. 

•	 The intensity of physician 

office visits, as measured by

medications prescribed or 

continued, imaging tests ordered

or provided, and time spent 

with physicians, also became 

increasingly concentrated on 

those aged 45 and over.

•	 Although most physicians

accept Medicare patients, 

acceptance of Medicare was 

higher among ophthalmologists 

and general surgeons than

among general or family 

practitioners, internists, and 

psychiatrists.

•	 Over the past 30 years, the 

specialty concentration of 

visits has shifted significantly.

In 1978, 62 percent of visits 

by patients aged 65 and over 

were to primary care physicians 

compared with 45 percent in 

2008. The percentage of visits 

to physicians with a medical or 

surgical specialty increased from

37 percent to 55 percent.

From 1998 to 2008, the U.S. population aged 65 and over increased by 15

percent, while the population aged 45 to 64 increased by 37 percent (1). The

proportion of persons aged 65 and over is expected to increase in the future

as the baby boomers, currently in the 45–64 age group, enter their elder years.

The federal Medicare program is the largest payer for health care for those 

aged 65 and over, and accounts for an increasing share of U.S. national health

expenditures—14 percent in 1978, 18 percent in 1998, and 20 percent in 2008

(2). Medicare has attempted to control expenditures through limiting payment

rates to physicians, resulting in generally lower Medicare physician fees

than private insurance fees (3). Despite this fact, most physicians accept new

Medicare patients (4), and Medicare spending is expected to continue to grow

(5). This report describes past trends in physician care provided to patients of

different ages, with particular attention paid to persons aged 45 and over.

Keywords: National Ambulatory Medical Care Survey • Medicare • physician 

office care

From 1998 to 2008, physician office visits and services 

became increasingly concentrated on middle-aged and 

older patients. 

0

20

40

60

80

100 65 years

and over

45–64 years

Under 45

years

1998 2008 1998 2008

1Based on the July 1, 2008 set of estimates of the civilian noninstitutionalized population of the United States as developed by the 

Population Division, U.S. Census Bureau.

2Based on data from the National Ambulatory Medical Care Survey, 1998 and 2008.

NOTE: Numbers may not add to totals because of rounding.

SOURCES: CDC/NCHS, National Ambulatory Medical Care Survey, 1998 and 2008 and the U.S. Census Bureau.

Figure 1. Percent distribution of population and physician office visits, by age: United States, 

1998 and 2008

U.S. population1 Office visits2 

Percent

12

67

21

12

62

26

24

52

25

27

43

30
NCHS Data Brief ■ No. 41 ■ August 2010

■  2  ■

•	 The percentage of the population aged 45 and over increased from 33 percent to 38 percent.

At the same time, the percentage of physician visits made by patients aged 45 and over 

increased from 49 percent to 57 percent (Figure 1).

•	 Patients aged 45 and over increased their share of total medications prescribed or continued

(from 60 percent to 70 percent) (Figure 2).

•	 Patients aged 45 and over also increased their share of imaging tests ordered or provided 

(from 52 percent to 66 percent). The largest increase in intensity was for imaging by those

aged 45–64; their share of all imaging ordered or provided increased from 26 percent to 36

percent.

•	 In addition, patients aged 45 and over increased their share of total time spent with a 

physician (from 50 percent to 59 percent).

•	 The increasing concentration of physician visits on older patients occurred because the

percentage of the population aged 45 and over increased and because visit rates among those

aged 45 and over increased. 

0

20

40

60

80

100

1998 2008

1The total number of medications was estimated by summing the total number of medications per visit (up to six) across all visits. 

2The total number of images was estimated by summing up to four types of images (CT scan, MRI, X-ray, ultrasound) per visit across all visits.

SOURCE: CDC/NCHS, National Ambulatory Medical Care Survey, 1998 and 2008.

Figure 2. Percent distribution of total medications, imaging, and time spent with physician, by patient age: National 

Ambulatory Medical Care Survey, 1998 and 2008

Medications prescribed 

or continued1 

Imaging ordered or 

provided2 

1998 2008 1998 2008

Minutes spent with 

physician

Percent

33

40

27

38

30

32

30

34

36

26

48

26

24

50

26

28

41

31

65 years

and over

45–64 years

Under 45

years
NCHS Data Brief ■ No. 41 ■ August 2010

■  3  ■

From 1998 to 2008, overall visit rates and visit rates where medications 

were prescribed or continued increased more for those aged 65 and over 

than for other age groups. 

• The office visit rate for patients aged 65 and over increased by 13 percent (from 6.1 to 

6.9 visits per person), and the visit rate where medications were prescribed or continued 

increased by 31 percent (from 4.2 to 5.5 visits per person) (Figure 3). 

• The visit rate was not different for the group aged 45–64; however, the medication rate 

increased in 2008 compared with 1998. 

SOURCE: CDC/NCHS, National Ambulatory Medical Care Survey, 1998 and 2008.

Figure 3. Annual rates of physician office visits and rates of visits with medications prescribed or continued: National 

Ambulatory Medical Care Survey, 1998 and 2008 Patient age in years

0 123456 7

Under

45

45–64

65 and

over

0123456 7

Under

45

45–64

65 and

over

Number of visits per person Number of visits with medications 

prescribed or continued per person

2008

1998

6.9

3.6

2.3

2.4

3.7

2.4

2.8

6.1

1.6

1.5

5.5

4.2
NCHS Data Brief ■ No. 41 ■ August 2010

■  4  ■

From 1998 to 2008, the largest increases in office visits for patients aged 

65 and over were for essential hypertension, cardiac dysrhythmias, and 

diabetes.

•	 Among all diagnoses, essential hypertension, cardiac dysrhythmias, and diabetes mellitus

accounted for the largest increases in number of visits from 1998 to 2008 (see table).

•	 The number of visits increased for disorders of lipoid metabolism by 150 percent, for

cardiac dysrhythmias by 139 percent, for essential hypertension by 62 percent, and for 

diabetes mellitus by 45 percent.

•	 Although not shown, some of these conditions were also top reasons for visit increases

among the group aged 45–64, including lipoid metabolism (increased by 161 percent),

essential hypertension (increased by 64 percent), and diabetes mellitus (increased by 17

percent).

Table. Primary diagnoses with the largest increase in number of visits for those aged 65 and over:

National Ambulatory Medical Care Survey, 1998 and 2008

Number of visits in thousan

Condition ICD–9–CM 

code(s)1

1998 2008 Increase Percent 

increase

Essential hypertension 401 14,015 22,655 8,640 6

Cardiac dysrhythmias 427 2,834 6,761 3,928 13

Diabetes mellitus 250 7,559 10,996 3,438 4

Disorders of lipoid metabolism 272 2,167 5,424 3,258 15

Actinic and seborrheic keratosis 702.0–702.1 2,627 4,130 1,503 5

Symptoms involving the urinary system 788 1,023 2,441 1,418 13

Coronary atherosclerosis 414 5,894 7,310 1,416 2

Malignant neoplasm of prostate 185 1,616 2,556 941 5

Retinal detachment and other retinal

disorders

361–363 1,859 2,662 803 43

Acquired hypothyroidism 244 586 1,369 783 13

1

ICD is International Classification of Diseases. For groupings of primary diagnosis codes, see National Health Statistics Reports, Number 8. Available

http://www.cdc.gov/nchs/data/nhsr/nhsr008.pdf.

SOURCE: CDC/NCHS, National Ambulatory Medical Care Survey, 1990 and 2008.
NCHS Data Brief ■ No. 41 ■ August 2010

■  5  ■

Most physicians accept new Medicare patients, but the percentage varies 

by physician specialty. 

•	 On average, 86 percent of physicians accepted new Medicare patients in 2008 (Figure 4).

•	 The percentage of physicians accepting new Medicare patients was highest among 

ophthalmologists (99 percent) and general surgeons (97 percent).

•	 The percentage accepting new Medicare patients was 82 percent for physicians in general 

or family practice, 80 percent for physicians in internal medicine, and 60 percent for 

psychiatrists.

Figure 4. Percentage of office-based physicians accepting new Medicare patients, by specialty: National Ambulatory 

Medical Care Survey, 2008 Physician specialty

0 20 40 60 80 100

Percent

Other1

Psychiatry

Orthopedic surgery

General surgery

Ophthalmology

Cardiovascular diseases

OB/gyn

Internal medicine

General/family practice

1Includes specialties not classified elsewhere, including dermatology, urology, and otolaryngology. Pediatricians are not included in this analysis.

NOTE: A small number of cases (less than 5% for each specialty) for which acceptance of Medicare patients was not known were assumed not to take Medicare 

patients. Among the specialties analyzed, an average of 86% of physicians accepted new Medicare patients. 

SOURCE: CDC/NCHS, National Ambulatory Medical Care Survey, 2008.

82

80

83

95

99

97

96

60

92
NCHS Data Brief ■ No. 41 ■ August 2010

■  6  ■

Among patients aged 65 and over, the percentage of visits to primary care 

specialists decreased from 1978 to 2008. 

•	 Over the longer period from 1978 to 2008, the percentage of visits that were to primary care 

specialists decreased from 62 percent in 1978 to 45 percent in 2008 for patients aged 65 and 

over (Figure 5).

•	 For those aged 65 and over, the percentage of visits to physicians with a medical or surgical

specialty increased from 37 percent to 55 percent. This pattern was also observed for 

patients aged 45–64.

Summary 

In 2008, physician office visits by those aged 45 and over accounted for a greater proportion of

all office visits than in 1998 (57 percent compared with 49 percent). Medications prescribed or

continued, imaging ordered or provided, and time spent with physician also became increasingly

concentrated on those aged 45 and over. For the same age group, physician visits became

increasingly concentrated on care provided by medical and surgical specialists and less on care

provided by primary care practitioners. 

In the future, the percentage of visits for those aged 65 and over will increase as the baby

boomers, currently aged 45–64, move into the 65 and over age group. Physician visits are

becoming increasingly focused on management of chronic conditions such as hypertension,

coronary atherosclerosis, and diabetes. Future changes in Medicare payment rates could affect

physician acceptance of Medicare and the distribution of care provided by specialty. An increased

focus on the quality and effectiveness of patient care could also affect the type and amount of care

provided. While this report describes past changes in office-based physician visits, both the aging

of the population and changes in the health care system will likely continue to alter the number

and intensity of physician office visits for elderly patients in future years.

0

20

40

60

80

100

1978 2008 1978 2008 1978 2008

NOTE: Numbers may not add to totals because of rounding.

SOURCE: CDC/NCHS, National Ambulatory Medical Care Survey, 1978 and 2008.

Figure 5. Percent distribution of physician office visits, by specialty type and patient age: National Ambulatory Medical 

Care Survey, 1978 and 2008

Under 45 years 45–64 years 65 years and over

Patient age by survey year

Percent

Medical

Surgical

Primary care

10

71

19

12

76

13

23

53

25

13

61

26

9

62

28

25

45

30
NCHS Data Brief ■ No. 41 ■ August 2010

■  7  ■

Definitions

Medications prescribed or continued: Includes prescription and over-the-counter drugs,

immunizations, allergy shots, anesthetics, chemotherapy, and dietary supplements that were

ordered, supplied, administered, or continued during the visits. In 1998, physicians could record

up to six medications, and in 2008, up to eight medications. Only the first six medications

mentioned in 2008 were analyzed for Figures 2 and 3 so that a comparison could be made to the

1998 data. 

Specialty type: This classification is used in Figure 5 and divides specialties into three major

categories: primary care, surgical, and medical. For a description of physician specialties included

in each of the three specialty types, see the 2008 National Ambulatory Medical Care Survey

(NAMCS) Public-use Data File Documentation.

Data source and methods

Data from the 1978, 1998, and 2008 NAMCS were used for these analyses. NAMCS is a national

probability sample survey of nonfederal office-based physicians in the United States conducted

by the Centers for Disease Control and Prevention’s National Center for Health Statistics,

Division of Health Care Statistics. The target universe of NAMCS includes visits made in

the United States to the offices of nonfederally employed physicians—excluding those in the

specialties of anesthesiology, radiology, and pathology—who were classified by the American

Medical Association and American Osteopathic Association as providing “office-based, patient

care.” 

NAMCS utilizes a multistage probability sample design involving samples of geographic primary

sampling units (PSUs), physician practices within PSUs, and patient visits within physician

practices. PSUs are counties, groups of counties, county equivalents, or for some PSUs in New

England, towns and townships. A sample weight is computed for each sample visit that takes

all stages of design into account. The survey data are inflated or weighted to produce unbiased

national annual estimates of physician office visits.

Due to hypothesized increases in health care utilization, differences among subgroups were

evaluated with one-tailed t tests using p < 0.05 as the level of significance. All comparisons

reported in the text are statistically significant unless otherwise indicated. Data analyses were

performed using the statistical packages SAS version 9.2 (SAS Institute, Cary, North Carolina),

SUDAAN version 10.0 (Research Triangle Institute, Research Triangle Park, North Carolina),

and STATA version 11.0 (College Station, Texas).

About the authors

Donald Cherry, Christine Lucas, and Sandra L. Decker are with the Centers for Disease Control

and Prevention’s National Center for Health Statistics, Division of Health Care Statistics.
NCHS Data Brief ■ No. 41 ■ August 2010

References

1. U.S. Census Bureau, Population Division. Population estimates based on

civilian noninstitutionalized population of United States. July 1, 2008.

2. Centers for Medicare & Medicaid Services, Office of the Actuary. NHE

historical and projections, 1965–2019. Available from: http://www.cms.

gov/NationalHealthExpendData/03_NationalHealthAccountsProjected.asp

[Accessed 6/29/10].

3. MedPAC. Report to the Congress: Medicare payment policy. 2010.

4. Hing E, Burt CW. Characteristics of office-based physicians and their

medical practices: United States, 2005–2006. National Center for Health

Statistics. Vital Health Stat 13(166). 2008.

5. Centers for Medicare & Medicaid Services. 2009 annual report of

the boards of trustees of the Federal Hospital Insurance and Federal

Supplementary Medical Insurance Trust Funds. Available from: https://www.

cms.gov/ReportsTrustFunds/downloads/tr2009.pdf [Accessed 6/29/10].

Suggested citation

Cherry D, Lucas C, Decker SL. Population

aging and the use of office-based physician

services. NCHS data brief, no 41.

Hyattsville, MD: National Center for Health

Statistics. 2010.

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

Division of Health Care Statistics

Jane E. Sisk, Ph.D., Director

U.S. D

Healt

Centers for Disease Control and Prevention

National Center for Health Statistics

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Hyattsville, MD 20782

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