Inactivity-Associated Medical Costs Among US Adults With Arthritis GUIJING WANG, 1 CHARLES G. HELMICK, 2 CAROL MACERA, 1 PING ZHANG, 2 AND MIKE PRATT 1 Objective. To analyze direct medical costs among US adults with arthritis and estimate the proportion associated with inactivity. Methods. In the 1987 National Medical Expenditure Survey, arthritis was defined using questions on self-reported, doctor-diagnosed arthritis or rheumatism. Physical activity was defined using a self-report question on level of activity. Inactivity-associated medical costs were derived by subtracting costs for active adults from costs for inactive adults after controlling for functional limitation. Results. Among 5,486 adults with arthritis, inactive persons had higher medical costs than did active persons in all demographic groups examined. In multivariate models adjusting for key covariates, the proportion of costs associated with inactivity averaged 12.4% ($1,250 in 2000 dollars) and ranged from 7.8% to 14.3% among various demographic groups. Conclusion. Inactivity-associated medical costs among persons with arthritis are considerable. Physical activity inter- ventions may be a cost-effective strategy for reducing the burden of arthritis. KEY WORDS. Arthritis; Costs; Economic; Physical activity. INTRODUCTION Arthritis and other rheumatic conditions are a major health problem in the United States, affecting 15% of the population (43 million persons) in 1990 and a projected 18.2% (60 million persons) by 2020 (1). Arthritis is a leading cause of chronic pain; is associated with a variety of health problems such as obesity, physical inactivity, and gastrointestinal bleeding related to use of nonsteroidal antiinflammatory drugs; is associated with poor health- related quality of life (2); and is the leading cause of disability in the US (1,3). More than 60% of persons with arthritis have limited physical activity to some extent (4). Disability related to arthritis among both working-age (18 – 64 years) and older (65 years) adults is significant, and trend data show disability rates for persons with ar- thritis are increasing, even when adjusted for age (5). The economic burden of arthritis is also enormous. Di- rect and indirect costs have been increasing in the US, from $21 billion (about 1% of the gross national product) in 1980 to $54.6 billion in 1988 and $65 billion in 1992 (6 – 8). About 23% of the costs were attributable to the direct costs of medical care; the remainder reflected indi- rect costs due to lost productivity (8). Because of the large economic and health burdens of arthritis, interest in arthritis as a public health problem is growing. Recently, the Arthritis Foundation, the Associa- tion of State and Territorial Health Officials, the Centers for Disease Control and Prevention (CDC), and 90 other organizations developed the National Arthritis Action Plan: A Public Health Strategy, which calls for developing intervention strategies to prevent the occurrence and pro- gression of arthritis (9). One recommended strategy is to decrease the high rate of physical inactivity among adults with arthritis, which is far higher than the rate among adults without arthritis (34.8% and 27.7%, respectively) (10). The physical inactivity associated with arthritis can have serious health consequences, such as loss of function and independence, increased risk for cardiovascular dis- ease, diminished quality of life, and unnecessary disability (11,12). The general health benefits of physical activity are well known; many recent studies have demonstrated the positive effects of physical activity on persons with arthri- tis as well (13–19). Experts now recognize that physical activity is an important element in the prevention and 1 Guijing Wang, PhD, Carol Macera, PhD, and Mike Pratt, MD, Division of Nutrition and Physical Activity; 2 Charles G. Helmick, MD, and Ping Zhang, PhD, Division of Adult and Community Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Con- trol and Prevention, Atlanta, Georgia. Address correspondence to Guijing Wang, PhD, DNPA, NCCDPHP, Centers for Disease Control and Prevention, 4770 Buford Highway, Atlanta, Georgia 30341-3717. E-mail: gbw9@cdc.gov Submitted for publication February 20, 2001; accepted May 31, 2001. ARTHRITIS CARE & RESEARCH 45:439 – 445, 2001 ORIGINAL ARTICLE © 2001, American College of Rheumatology Published by Wiley-Liss, Inc. 439