Cheng Y, Macera CA, Davis DR, Ainsworth BE, Troped PJ, Blair SN. Physical activity and self-reported, physician-diagnosed osteoarthritis: is physical activity a risk factor? J Clin Epidemiol 2000;53:315–322.
ObjectiveIs Physical Activity a Risk Factor for Osteoarthritis?
To evaluate the relation between physical activity and the incidence of self-reported, physician-diagnosed osteoarthritis of the knee or hip.
DesignIs Physical Activity a Risk Factor for Osteoarthritis?
SettingIs Physical Activity a Risk Factor for Osteoarthritis?
Cooper Clinic, Dallas, Texas.
ParticipantsIs Physical Activity a Risk Factor for Osteoarthritis?
The study included persons ≥20 years of age who were examined at the clinic between 1970 and 1995. Persons who had a diagnosis of osteoarthritis before the baseline visit and persons for whom follow-up information on osteoarthritis was missing were excluded. 12,888 men (76%; median age, 44 years; mean follow-up, 10.9 years) and 4,073 women (24%; median age, 4.3 years mean follow-up; 9.9 years) were included in the study.
Assessment of risk factorsIs Physical Activity a Risk Factor for Osteoarthritis?
Physical activity was assessed by self-reported regular exercise patterns. Sedentary persons (no regular exercise) were the reference group. Regular exercise comprised 4 groups, high, moderate, and low walking or jogging (>20, ≥10 ≤ 20, and <10 miles per week, respectively), and other regular physical activity. Lifestyle behaviors and physical characteristics were obtained from the baseline questionnaire and medical examination.
Main outcome measureIs Physical Activity a Risk Factor for Osteoarthritis?
Participants reported the presence or absence of physician-diagnosed osteoarthritis of the knee and/or hip in the 1990 or 1995 surveys. A substudy showed substantial agreement between self-reported incidence and medical record documentation (kappa = 0.68).
Main resultsIs Physical Activity a Risk Factor for Osteoarthritis?
Among participants ≥50 years of age, the incidence of osteoarthritis was higher for women than men (7.0 vs. 4.9 per 1,000 person-years; p = 0.001), whereas for women and men <50 years, the incidence was similar (2.7 vs. 2.3 per 1,000 person-years, respectively; p = 0.116). Among men, only the highest level of physical activity was associated with osteoarthritis (hazard ratio [HR], 1.6; 95% CI, 1.1 to 2.3; p for trend, 0.1669). Significant trends were found for body mass index, past cigarette smoking, high alcohol use, and older age. Among women there was no association between osteoarthritis and regular physical activity (p for trend = 0.896). Significant trends were found for body mass index, older age, and caffeine consumption. In multivariate analysis, a high level of physical activity was associated with osteoarthritis among men under age 50 years (HR, 2.4; CI, 1.5 to 3.9) but not among older men (HR, 1.2; CI, 0.6 to 2.3). Greater body mass index and heavy alcohol consumption were also associated with osteoarthritis among younger but not older men. Among older and younger women no significant associations of osteoarthritis with physical activity were found, but greater body mass index was related to osteoarthritis in both age groups.
ConclusionIs Physical Activity a Risk Factor for Osteoarthritis?
Osteoarthritis of the knee and/or hip was not associated with level of physical activity except among men under 50 years of age who walked or jogged more than 20 miles per week.
Source of funding (in part): National Institute on Aging.
For article reprint: C. A. Macera, PhD, National Center for Chronic Disease Prevention, Centers for Disease Control and Prevention, 4770 Buford Highway, Atlanta, GA 30341, U.S.A. E-mail: email@example.com
CommentaryIs Physical Activity a Risk Factor for Osteoarthritis?
Despite extensive investigation, there is still uncertainty on whether there is a direct relationship between various forms of physical exercise and the onset, or acceleration, of osteoarthritis. 1 In many studies, potential confounding variables such as age, gender, ethnicity, body weight, smoking, and alcohol consumption make it difficult to determine the presence of unequivocal causal linkages. Moreover, several of the studies that have addressed the exercise-arthritis conundrum have been inconclusive because of flaws in their methods and execution.
In the prospective study by Cheng et al. a large sample of physically active men and women were followed over a 10-year period. The study design was well suited to addressing the investigators' research question, the statistical analysis was sound, and the conclusions interpreted the data appropriately.
The authors of the study draw attention to some of the limitations of their data. Principal among these was the reliance on self-report by participants in the study. Also, the generalizability of the findings was somewhat compromised by the predominance of a well-educated, upper socioeconomic population in the study cohort. However, regardless of certain imperfections in study methods, the investigators demonstrated that walking or running 20 miles or more per week is associated with osteoarthritis in younger men (i.e., those in the 20-to-49-year age range). This finding needs to be seen in the context of other studies, where such clear associations have not been as evident. 1 Given the available evidence, does physical exercise, especially running, cause osteoarthritis? The definitive answer to this vexing question remains elusive.