Prevalence of Doctor-Diagnosed Arthritis and Arthritis-Attributable Activity Limitation --- United States, 2003--2005

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Arthritis is highly prevalent among U.S. adults, the leading cause of disability (1), and associated with substantial activity limitation, work disability, reduced quality of life, and high health-care costs (2--4). As the population ages, arthritis is expected to affect an estimated 67 million adults in the United States by 2030 (5). This report updates estimates of the national prevalence of doctor-diagnosed arthritis and arthritis-attributable activity limitation in the adult U.S. population, using data from the National Health Interview Survey (NHIS) for 2003--2005. The findings indicated that an estimated 21.6% of the adult U.S. population (46.4 million persons) had doctor-diagnosed arthritis, and 8.3% (17.4 million) had arthritis-attributable activity limitations. Public and private health agencies should promote measures to increase the availability of evidence-based arthritis prevention and management interventions.

NHIS is an annual, household-based survey of a representative sample of the U.S. civilian, noninstitutionalized population, using in-person interviews. This study used the sample adult core component of the NHIS survey, which collects information on adults aged >18 years residing in selected households. In 2003, 2004, and 2005, the sample sizes were 30,852, 31,326, and 31,428, respectively, for the adult core component, and the final response rates were 74.2%, 72.5%, and 69.0%, respectively. Respondents were defined as having doctor-diagnosed arthritis if they answered "yes" to the question, "Have you ever been told by a doctor or other health professional that you have some form of arthritis, rheumatoid arthritis, gout, lupus, or fibromyalgia?" Those who answered "yes" were asked, "Are you limited in any way in any of your usual activities because of arthritis or joint symptoms?" Persons responding "yes" to both questions were defined as having an arthritis-attributable activity limitation.

For this study, prevalence estimates are presented overall and by sex, age group, race/ethnicity, education level, body mass index (BMI)* category, and physical activity level. Physical activity level of respondents was determined from six questions that asked about frequency and duration of participation in leisure-time activities of moderate and vigorous intensity; those reporting no participation in such activities were classified as inactive, and all others as active. Estimates were calculated by using combined data from 2003--2005 and applying an annual average weighting; 95% confidence intervals (CIs) were calculated using sample design factors and statistical software to account for the multistage probability sample. To facilitate comparisons between demographic subgroups, estimates were age adjusted to the standard 2000 U.S. population (6). All differences noted in this report are statistically significant (p<0.05) with nonoverlapping 95% CIs.

In unadjusted analyses for 2003--2005 (Table), the prevalence of doctor-diagnosed arthritis among adults was estimated at 21.6%, or 46.4 million persons. Prevalence was higher among women (25.4%) compared with men (17.6%), older age groups (50% for persons aged >65 years and 29.3% for persons aged 45--64 years) compared with younger age groups (7.9% for persons aged 18--44 years), and non-Hispanic whites (24.3%) compared with non-Hispanic blacks (19.2%) and Hispanics (11.4%). Prevalence also was higher among those who were obese (31.6%) or overweight (21.7%) compared with those who were normal weight or underweight (16.3%) and among those who were physically inactive (25.0%) compared with those who were physically active (19.5%). After adjustment for age, all of these differences (except among age groups) were slightly attenuated but remained significant, with the exception of differences between non-Hispanics whites (22.6%) and non-Hispanic blacks (21.4%).

Unadjusted analyses for arthritis-attributable activity limitation among adults indicated an estimated overall prevalence of 8.3%, or 17.4 million persons, with differences among groups that were similar to those for doctor-diagnosed arthritis prevalence. The exception was a similar prevalence for non-Hispanic blacks (8.8%) and non-Hispanic whites (8.9%). Age-adjusted analyses identified differences among groups that were similar to the unadjusted figures, except that prevalence among non-Hispanic blacks (10.0%) significantly exceeded that for non-Hispanic whites (8.4%).

In unadjusted analyses of all adults reporting arthritis, 38.8% reported arthritis-attributable activity limitation (Table). Proportions were significantly higher among women (40.1%) compared with men (36.6%) and among non-Hispanic blacks (45.7%) and Hispanics (43.8%) compared with non-Hispanic whites (37.4%). Persons with arthritis and activity limitations also were more likely to have less than a high school education (50.6% versus 36.1%) or to be obese (46.4% versus 34.3% underweight/normal weight) or physically inactive (52.6% versus 31.3%). Age-adjusted analyses eliminated the significant difference between men and women, but did not otherwise change the results.

Reported by: J Hootman, PhD, J Bolen, PhD, C Helmick, MD, G Langmaid, Div of Adult and Community Health, National Center for Chronic Disease Prevention and Health Promotion, CDC.

Editorial Note:

The findings in this report indicate that 21.6% (46.4 million) of U.S. adults reported doctor-diagnosed arthritis, and 8.3% (17.4 million) reported arthritis-attributable activity limitation during 2003--2005. This represents an increase from 2002, when an estimated 20.8% (42.7 million) reported doctor-diagnosed arthritis and 7.8% (16.0 million) reported arthritis-attributable activity limitation (2). The increase in both the prevalence of doctor-diagnosed arthritis and arthritis-attributable activity limitation is consistent with future projections, largely based on the aging of the population (5). However, in 2003, the NHIS transitioned to a weighting structure based on the 2000 U.S. Census population; therefore, interpretation of this increased prevalence should be made with caution. Additional years of data are needed to determine whether these growth trends will be lasting.

Disparities exist with regard to arthritis and activity limitations. Women, older adults, persons with little education, or those who are obese, overweight, or physically inactive are more likely affected. In unadjusted analyses, doctor-diagnosed arthritis was less prevalent among non-Hispanic blacks and Hispanics than among non-Hisipanic whites; however, both groups reported greater proportions of persons with arthritis-attributable activity limitation.

In contrast to previous estimates of arthritis prevalence based on 1 year of data, prevalences for a 3-year period were used to reduce the year-to-year fluctuation that can result from smaller sample sizes from a single year. This approach might provide more reliable estimates, especially for smaller groups such as certain racial/ethnic populations and older adults.

The findings in this report are subject to at least three limitations. First, doctor-diagnosed arthritis was self-reported and not confirmed by a health-care professional, although self-report of arthritis has been determined valid for surveillance purposes (7). Second, the cross-sectional study design does permit determining the temporal sequence of arthritis onset and selected characteristics (e.g., obesity or physical inactivity). However, other studies have identified excess body weight as a risk factor for incident osteoarthritis, the most common type of arthritis, and physical activity has been determined to prevent or delay onset of functional limitation and disability among adults with osteoarthritis (8). Finally, certain factors that might contribute to differences in arthritis prevalence (e.g., history of joint injury or comorbid conditions such as cardiovascular disease, diabetes, or depression) were not analyzed.

Population-based national surveillance of arthritis prevalence and associated effects such as arthritis-attributable activity limitation are important to identify groups at greatest risk, target interventions, and measure progress toward achieving national health objectives (9). Currently, the CDC Arthritis Program is focusing on expanding the availability of evidence-based physical-activity and self-management interventions proven to reduce pain and improve function among adults with arthritis. Such interventions include those related to safe physical activity for persons with arthritis (e.g., Arthritis Foundation's Exercise Program, Arthritis Foundation's Aquatics Program, and EnhanceFitness) and self-management education (e.g., Arthritis Foundation's Self-Help Course and the Chronic Disease Self-Management Program). In addition, the CDC Arthritis Program is working with 35 state health department programs and various local chapters of the Arthritis Foundation to disseminate a health communications campaign designed to promote greater physical activity among adults with arthritis. The campaign, "Physical Activity. The Arthritis Pain Reliever," was developed to target an audience of low-income men and women aged >45 years with arthritis. A similar campaign targeted to Spanish-speaking adults, "Buenos Dias Artritis," is being developed and tested. Further research is needed to investigate possible underlying reasons for the differences among groups in arthritis prevalence and activity limitation and to develop more targeted solutions to improve the quality of life for all adults with arthritis, particularly among those most affected.

References

* BMI was calculated using self-reported weight and height as follows: weight (kg) / height (m²). Categories were defined as follows: underweight/normal weight, <24.9; overweight, 25.0--29.9; and obese, >30.0.

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