Projections of US prevalence of arthritis and associated activity limitations

Authors


Abstract

Objective

To update the projected prevalence of self-reported, doctor-diagnosed arthritis and arthritis-attributable activity limitations among US adults ages 18 years and older from 2005 through 2030.

Methods

Baseline age- and sex-specific prevalence rates of arthritis and activity limitation, using the latest surveillance case definitions, were estimated from the 2003 National Health Interview Survey, which is an annual, cross-sectional, population-based health interview survey of ∼31,000 adults. These estimates were used to calculate projected arthritis prevalence and activity limitations for 2005–2030 using future population projections obtained from the US Census Bureau.

Results

The prevalence of self-reported, doctor-diagnosed arthritis is projected to increase from 47.8 million in 2005 to nearly 67 million by 2030 (25% of the adult population). By 2030, 25 million (9.3% of the adult population) are projected to report arthritis-attributable activity limitations. In 2030, >50% of arthritis cases will be among adults older than age 65 years. However, working-age adults (45–64 years) will account for almost one-third of cases.

Conclusion

By 2030, the number of US adults with arthritis and its associated activity limitation is expected to increase substantially, resulting in a large impact on individuals, the health care system, and society in general. The growing epidemic of obesity may also significantly contribute to the future burden of arthritis. Improving access and availability of current clinical and public health interventions aimed at improving quality of life among persons with arthritis through lifestyle changes and disease self-management may help lessen the long-term impact.

Arthritis and other rheumatic conditions already represent the leading cause of disability in the US (1) and are among the most common chronic disease problems in the country, with almost 43 million adults affected (2). The already large clinical burden (36 million ambulatory care visits and 750,000 hospitalizations in 1997) (3, 4) is likely to increase because the prevalence of arthritis is highest in older adults, and the proportion of adults ≥65 years of age is expected to increase at least 7% by 2030, raising the total to 20% of the population (5). Therefore, predicting the future prevalence and impact of arthritis is important for planning future clinical and public health needs as well as resource allocation.

The projections now being used (5) were made without use of currently recommended surveillance case definitions for self-reported arthritis, focused only on those ages 65 and older, and were obtained using state-based data sources that may not accurately reflect national prevalence. The purpose of this study was to update the projected 2005–2030 prevalence of self-reported, doctor-diagnosed arthritis and arthritis-attributable activity limitation for all adults ages 18 years and older, using the most recent national-level data source and current validated surveillance definitions.

METHODS

The National Health Interview Survey (NHIS) is an annual multipurpose health survey conducted by the National Center for Health Statistics. The NHIS uses a complex stratified sample design to collect data on ∼36,000 households, and provides national estimates of a broad range of health measures, including self-reported diseases and conditions, for the noninstitutionalized civilian US population (6).

The Sample Adult Core contains detailed health information on 1 adult who was randomly selected from each sampled household. In 2003, ∼31,000 adult respondents in the Sample Adult Core were asked questions on arthritis prevalence and impact. For the current study, self-reported doctor-diagnosed arthritis was defined as an answer of “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 fibromylagia?” This case definition has been developed, cognitively tested, and validated, and is currently recommended for use in public health surveillance of arthritis (7). Arthritis-attributable activity limitation was defined as an answer of “yes,” by a patient with doctor-diagnosed arthritis, to the question “Are you now limited in any way in any of your usual activities because of arthritis or joint symptoms?”

Age- and sex-specific prevalence rates for doctor-diagnosed arthritis and arthritis-attributable activity limitation were calculated for all adults and weighted to the US population, using the adult sample weight provided by the National Center for Health Statistics for use with the NHIS and SUDAAN statistical software (Table 1). Projected population estimates (middle series) for 2005–2030, in 5-year intervals, were obtained from the US Census Bureau (8), and applied to the age- and sex-specific prevalence rates calculated from the 2003 NHIS. Prevalence was summed across ages and sexes, to produce the final projected number of adults with doctor-diagnosed arthritis and with arthritis-attributable activity limitation for each year.

Table 1. Age- and sex-specific weighted prevalence estimates of self-reported, doctor-diagnosed arthritis and arthritis-attributable activity limitation among US adults, from the 2003 National Health Interview Survey
Sex, age, yearsDoctor-diagnosed arthritisArthritis-attributable activity limitation
No. in thousands% rateNo. in thousands% rate
Men    
 18–443,3366.101,0551.93
 45–648,50325.772,8658.66
 65+5,85240.722,10414.51
 Total17,69217.346,0245.91
Women    
 18–445,2979.501,7623.16
 45–6412,03534.374,55412.95
 65+10,76954.854,55523.06
 Total28,10225.4510,8719.86
Total population45,79321.5616,8957.96

RESULTS

In 2003, an estimated 45.8 million adults (21.6%) reported having doctor-diagnosed arthritis (Table 1). This number is projected to increase from 47.8 million in 2005 to nearly 67 million (25%) by 2030 (Table 2). Women will account for 61% (40.9 million) of the arthritis cases in 2030 (Figure 1A). Adults over age 65 years will account for 37.2% of arthritis cases in 2005, growing to >51% of cases by 2030 (Figure 1B). By 2030, nearly one-third of adults ages 45–64 years, who are integral contributors to the work force, will have arthritis.

Table 2. Estimated US adult population and projected prevalence of doctor-diagnosed arthritis and arthritis-attributable activity limitations among adults ages 18 years and older, US, 2005–2030*
YearEstimated US population, in thousandsProjected prevalence of doctor-diagnosed arthritis, in thousandsProjected prevalence of arthritis-attributable activity limitations, in thousands
  • *

    Weighted percentages for age- and sex-specific rates of doctor-diagnosed arthritis and arthritis-attributable activity limitation were calculated from the % rate data shown in Table 1.

2005216,09647,83817,610
2010227,76251,87919,117
2015238,15455,72520,601
2020247,77559,40922,052
2025257,46963,20923,565
2030267,85666,96925,043
Figure 1.

A, Projected prevalence of doctor-diagnosed arthritis in the US, 2005–2030, by sex. B, Projected prevalence of doctor-diagnosed arthritis in the US, 2005–2030, by age.

Approximately 16.9 million US adults (7.9%) reported arthritis-attributable activity limitation in 2003 (Table 1). This is projected to increase to 17.6 million by 2005 and to 25 million (9.3% of the US adult population) by 2030 (Table 2). In 2030, of adults with arthritis-attributable activity limitation, 64% will be women and 54% will be age 65 years and older (Figures 2A and B).

Figure 2.

A, Projected prevalence of arthritis-attributable activity limitations in the US, 2005–2030, by sex. B, Projected prevalence of arthritis-attributable activity limitations in the US, 2005–2030, by age.

DISCUSSION

Nearly 67 million adults are projected to have self-reported, doctor-diagnosed arthritis by the year 2030, with half of the cases being in older adults. In addition, 25 million will have arthritis-attributable activity limitations. Given the methods used, these projected increases depend entirely upon the projected increase in the size and age of the US population. This is a reasonable approach, because other methods, such as using projections of underlying risk factors, are difficult or impossible to undertake given the structure of current data sources. These projections are likely conservative because they assume that the current age- and sex-specific prevalence rates of arthritis and activity limitation will remain stable and that the prevalence of associated risk factors, such as obesity, will remain unchanged. Given the current epidemic of obesity in this country, however, there is considerable potential for the prevalence and impact of arthritis to be even higher. These estimates do not take into account the substantial number of adults with possible arthritis, i.e., those who have chronic joint symptoms compatible with arthritis but have not been diagnosed by a health care provider. However, improving secular trends in factors associated with arthritis prevalence (e.g., occupation type) and disability (e.g., comorbid conditions) could dampen these projected increases.

The arthritis-related clinical and health care system burden will increase substantially over the next 30 years. This may require training more specialists in rheumatology and orthopedics, especially to address regional gaps in the availability of services (9, 10). Because primary care providers treat the majority of outpatients with arthritis and other rheumatic conditions (3), their skills in assessing and treating musculoskeletal conditions may need to be improved (11). Some of these issues may be addressed by better undergraduate training in basic musculoskeletal medicine skills, competencies, and care knowledge (12), as well as focused, evidence-based continuing medical education offerings.

The societal burden of arthritis will increase, as well. Since arthritis is associated with chronic pain, functional limitations, disability, absenteeism, and work-related disability, the large numbers of adults affected in the next 30 years will only add to the already large impact of the disease. In 2003, an estimated 16.9 million US adults reported arthritis-attributable activity limitation, and 8 million reported that arthritis affected their work (2). With the aging of the population, experts anticipate that more adults over age 65 years will continue to work, possibly well into their 70s (13), meaning that two-thirds of the working-age population could potentially have arthritis by 2030, and many of those will have activity limitations. Employers may need to address ergonomic issues, injury prevention, and work place accommodations for these employees. Health insurance costs may also increase for employers as well as individuals.

Finally, the increasing public health system burden of arthritis will require promoting and disseminating community-based interventions that complement clinical medical care and can improve or maintain quality of life among people with arthritis. Such interventions include the promotion of lifestyle modifications and self-management education for arthritis, which have been shown to be effective at reducing pain, improving function, and decreasing both disability and health care utilization. For example, reaching and maintaining a normal body weight may reduce the risk of incident knee osteoarthritis as well as influence disease progression (14). Engaging in moderate physical activity is known to reduce pain up to 30%, improve function, and reduce the risk of disability almost 50% without increasing symptoms or disease progression (15, 16).

Currently available community-based physical activity and self-management education programs, such as the Arthritis Foundation/YMCA Aquatics Program and People with Arthritis Can Exercise program, have been proven to be effective in pain management, improved mobility, and self-efficacy, and are appropriate for people with most types of arthritis (16). The Arthritis Self-Help Course, also offered through the Arthritis Foundation, is a 6-week self-management education program that has been shown to reduce pain and physician visits, while improving mental health (16). Despite the benefits of these community-based programs, <1% of people with arthritis who may benefit from these programs actually access them (16).

The large increase in projected numbers of adults with arthritis represents a challenge to the health care and public health systems. That impact may be lessened by improving training of primary care providers, and increasing access to and availability of current clinical and public health arthritis interventions aimed at improving quality of life through lifestyle changes and disease self-management.

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