Prevalence and Most Common Causes of Disability Among Adults --- United States, 2005

Since 1994, disability-related costs for medical care and lost productivity have exceeded an estimated $300 billion annually in the United States (1). To update previous reports on the prevalence and most common causes of disability among adults (2), CDC and the U.S. Census Bureau analyzed the most recent data from the Survey of Income and Program Participation (SIPP). This report summarizes the findings of that analysis, which indicated that the prevalence of disability in 2005 (21.8%) remained unchanged from 1999 (22.0%); however, because of the aging of the population, particularly the large group born during 1946--1964 ("baby boomers"), the estimated absolute number of persons reporting a disability increased 7.7%, from 44.1 to 47.5 million. The three most common causes of disability continued to be arthritis or rheumatism (affecting an estimated 8.6 million persons), back or spine problems (7.6 million), and heart trouble (3.0 million). Women (24.4%) had a significantly higher prevalence of disability compared with men (19.1%) at all ages. For both sexes, the prevalence of disability doubled in successive age groups (18--44 years, 11.0%; 45--64 years, 23.9%; and ≥65 years, 51.8%). The number of adults reporting a disability likely will increase, along with the need for appropriate medical and public health services, as more persons enter the highest risk age group (≥65 years). To accommodate the expected increase in demand for disability-related medical and public health services, expanding the reach of effective strategies and interventions aimed at preventing progression to disability and improving disability management in the population is necessary.

SIPP is a longitudinal panel survey conducted by the U.S. Census Bureau that represents the civilian noninstitutionalized population living in the United States and excludes persons living in institutions (e.g., nursing homes). The sampling frame for SIPP selection is based on the Census Bureau's Master Address File of every address in the United States and is stratified by socioeconomic and demographic characteristics from the decennial census. All members of selected households are invited to participate voluntarily in a SIPP panel. Panels are active for 2.5--4 years, during which computer-assisted in-person interviews are conducted in 4-month intervals (waves) that include supplemental questionnaires (topic modules).

Data used for this report are cross-sectional findings from the Wave 5 disability topical module (fielded June--September 2005) of the 2004 SIPP panel and are the most recent available disability data (3). During Wave 5, a total of 70,312 persons aged ≥18 years from 37,400 households (representing 82.6% of eligible households) were interviewed. All household members aged ≥18 years were questioned for this analysis; proxy response was allowed for panel members unavailable at the time of interview. Responses were weighted to population controls (the actual population at the time of interview), and sampling weights for cross-sectional analysis of Wave 5 were applied to generate national estimates of disability prevalence and cause,* accounting for the complex survey design, and adjusting, in part, for undercoverage (3,4). All estimates in this report have been adjusted for sample size, clustering, survey design, and other features.† Differences in the prevalence of disability by sex across age groups and other comparisons were assessed by z-test and considered statistically significant if the 95% confidence interval (CI) of the difference excluded zero (p<0.05) (4).

Participants were asked, "Because of a physical or mental health condition, [do you] have difficulty doing any of the following by yourself?" and queried about various activities (Table 1). Disability was defined as a "yes" response to at least one of the following limitation categories: 1) use of an assistive aid (cane, crutches, walker, or wheelchair), 2) difficulty performing activities of daily living (ADLs) or instrumental activities of daily living (IADLs), or specified functional activities,§ 3) one or more selected impairments,¶ or 4) limitation in the ability to work around the house or at a job or business. Persons reporting any of these limitations (except those with only "use of an assistive aid" or "selective impairments") also were asked "Which condition or conditions cause these difficulties?" and shown a list of 30 conditions (Table 2) from which they were asked to identify the cause of their disability.** Respondents indicating more than one condition were asked to identify a main condition (3). For this report, "cause of disability" refers to the health condition the respondents identified as the main cause of their disability.

In 2005, the prevalence of self-reported disabilities among civilian noninstitutionalized U.S. adults aged ≥18 years was 21.8%, and the total estimated population reporting a disability was 47.5 million. The proportion of persons reporting a disability increased with age (18--44 years, 11.0%; 45--64 years, 23.9%; and ≥65 years, 51.8%) (Table 1) and was significantly higher among women (24.4%; CI = 23.7--25.1) compared with men (19.1%; CI = 18.5--19.7) overall and in all age groups (Figure). The estimated population with a disability among persons aged 45--64 years (17.3 million) was not statistically different (p=0.081) than among those aged ≥65 years (18.1 million). The most commonly reported disability category was "difficulty in specified functional activities," a collection of seven subcomponent measures that affected 17.3% of adults. The most commonly reported subcomponent measures were difficulty walking three city blocks (10.3%; estimated population affected = 22.5 million) and climbing a flight of stairs (10.0%; estimated population affected = 21.7 million) (Table 1).

A total of 94% of SIPP participants self-reporting a disability self-reported a cause. Arthritis or rheumatism was the most common cause of disability overall (19.0%; estimated population affected = 8.6 million) and for women (24.3%). Back or spine problems was the second most common cause of disability overall (16.8%, estimated population affected = 7.6 million) and the most common cause for men (16.9%). Heart trouble was the third most common cause of disability overall (6.6%, estimated population affected = 3.0 million) and for both sexes (8.4% men, 5.4% women) (Table 2).

Reported by: MW Brault, US Census Bureau. J Hootman, PhD, CG Helmick, MD, KA Theis, MPH, Div of Adult and Community Health, National Center for Chronic Disease Prevention and Health Promotion; BS Armour, PhD, Div of Human Development and Disability, National Center on Birth Defects and Developmental Disabilities, CDC.

Editorial Note:

This analysis determined that the estimated percentage of U.S. adults reporting a disability has not changed since 1999, when, using the same survey and definitions, 22.0% of adults reported having a disability (2). Reasons for this leveling off likely include a better educated public, improved medical interventions, increased public health attention to behavior modifications (e.g., tobacco use), and increased access to assistive technology among the most advantaged socioeconomic groups (5,6).

Although the percentage has not changed, this analysis and other studies have determined that the absolute number of persons in the U.S. population reporting disabilities is increasing because of a rise in the at-risk population (1--3). The analysis in this report determined that, as of 2005, the number of baby boomers (persons aged 45--64 years) reporting disabilities had already become equal to the number of persons aged ≥65 years in the U.S. population reporting disabilities, even though they have a lower prevalence of disability as a group. After baby boomers enter the ≥65 years age group, which has a much higher risk for disability, the absolute number of persons affected likely will increase substantially. This might be particularly true for women, who, consistent with previous findings (1,3), report disability more often than men at all ages and also have a longer life expectancy. The added number of persons reporting disabilities is likely to place more demands on the health-care and public health systems (e.g., an increased need for additional health-care providers trained in musculoskeletal conditions).††

The findings in this report are subject to at least four limitations. First, because SIPP excludes persons residing in institutions, estimates of disability prevalence are conservative, especially among persons aged ≥65 years, who have higher rates of institutionalization. Second, statistics from surveys are subject to sampling and nonsampling error (e.g., respondent interpretation of question meaning); statistical weighting procedures might not completely control for all sources of nonsampling error, and some bias might remain.§§ However, all comparisons presented in this report have taken sampling error into account using statistical weighting procedures (4) and exceed U.S. Census Bureau minimal standards for statistical significance. Third, identifying the main cause of disability might be difficult for persons with multiple chronic conditions (2,3). Finally, the definition of disability used, although consistent with previous reports (2,3), might not be directly comparable to disability definitions used for other purposes, (e.g., qualification for Supplemental Security Income benefits).

By 2030, the number of U.S. adults aged ≥65 years will approximately double from current numbers to about 71 million. The implications of this growing number of older adults include unprecedented demands on public health and senior services and the nation's health-care system. For example, greater numbers of trained professionals will be needed to expand the reach of effective community-based programs to mitigate the effects of disability. Modifiable lifestyle characteristics (e.g., physical inactivity, obesity, and tobacco use) are major contributors to the most common causes of disability, and sometimes stem from a primary disabling condition (7). Widespread use of effective, population-based approaches to increase physical activity, reduce obesity and tobacco use, and provide health promotion education programs for persons with an existing disability¶¶ can reduce the incidence of various associated chronic conditions, prevent some disabilities, and reduce the severity of others. Regular physical activity is effective in reducing morbidity resulting from heart disease and reducing or eliminating multiple associated risk factors (8,9). Physical activity also has been shown to prevent episodes of back problems (10), reduce pain, improve physical function, and delay disability among adults with arthritis (8). Health-care providers should consider early referral to interventions that can prevent or reduce severity of disability for patients at high risk for disability (e.g., women and persons with chronic musculoskeletal conditions).

References

1. US Department of Health and Human Services. The Surgeon General's call to action to improve the health and wellness of persons with disabilities. Washington, DC: US Department of Health and Human Services, Office of the Surgeon General; 2005.
2. CDC. Prevalence of disabilities and associated health conditions among adults---United States, 1999. MMWR 2001;50:120--5.
3. Brault, M. Americans with disabilities: 2005, current population reports, P70-117, Washington, DC: US Census Bureau; 2008.
4. US Census Bureau. Source and accuracy statement for the Survey of Income and Program Participation 2004 Wave 1--Wave 12 public use files. Washington, DC: US Department of Commerce, US Census Bureau; 2009. Available at http://www.census.gov/sipp/sourceac/s&a04_w1tow12(s&a-9).pdf.
5. Schoeni RF, Martin LG, Andreski PM, Freedman VA. Persistent and growing socioeconomic disparities in disability among the elderly: 1982--2002. Am J Public Health 2005;95:2065--70.
6. Schoeni RF, Freedman VA, Wallace RB. Persistent, consistent, widespread, and robust? Another look at recent trends in old-age disability. J Gerontol B Psychol Sci Soc Sci 2001;56:S206--18.
7. Institute of Medicine. Workshop on disability in America: a new look. Washington, DC: National Academies Press; 2006.
8. US Department of Health and Human Services. Physical Activity Guidelines Advisory Committee. Physical Activity Guidelines Advisory Committee report, 2008. Washington, DC: US Department of Health and Human Services; 2008.
9. Li TY, Rana JS, Manson JE, et al. Obesity as compared with physical activity in predicting risk of coronary heart disease in women. Circulation 2006;113:499--506.
10. Bigos SJ, Holland J, Holland C, Webster JS, Battie M, Malmgren JA. High-quality controlled trials on preventing episodes of back problems: systematic literature review in working-age adults. Spine J 2009;9:147--68.

Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of Health and Human Services. References to non-CDC sites on the Internet are provided as a service to MMWR readers and do not constitute or imply endorsement of these organizations or their programs by CDC or the U.S. Department of Health and Human Services. CDC is not responsible for the content of pages found at these sites. URL addresses listed in MMWR were current as of the date of publication.

All MMWR HTML versions of articles are electronic conversions from typeset documents. This conversion might result in character translation or format errors in the HTML version. Users are referred to the electronic PDF version (http://www.cdc.gov/mmwr) and/or the original MMWR paper copy for printable versions of official text, figures, and tables. An original paper copy of this issue can be obtained from the Superintendent of Documents, U.S. Government Printing Office (GPO), Washington, DC 20402-9371; telephone: (202) 512-1800. Contact GPO for current prices.

**Questions or messages regarding errors in formatting should be addressed to mmwrq@cdc.gov.

Date last reviewed: 4/30/2009