Decreased Osteoarthritis Risk in Experienced Marathon Runners: Commentary on an article by Danielle Y. Ponzio, MD, et al.

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In their study, Ponzio et al. suggest that marathon runners have less self-reported physician-diagnosed knee and hip arthritis than a matched U.S. population.
A marathon is a long running distance: 42 km or 26.2 miles. A large number of active marathon runners run many miles a week in their preparation for a race. In the present study, Ponzio et al. distributed a health survey to 675 active, international marathoners who all ran at least 10 miles a week. The hip and knee arthritis prevalence in the U.S. runners was compared with National Center for Health Statistics prevalence estimates for a matched group of the U.S population. The marathoners in the present study were serious runners: at a mean age of 48 years, they ran a mean distance of 36 miles weekly and completed a mean number of 76 marathons. Forty-seven percent self-reported hip or knee pain, and 8.9% self-reported physician-diagnosed hip or knee arthritis. For the U.S. marathoners, the arthritis prevalence was 8.8%, significantly lower than a matched U.S. population at 17.9%. In this group, age, female sex, and surgical history were independent risk factors for arthritis, but, surprisingly, there were no significant risks associated with running duration, intensity, mileage, or number of marathons completed.
The findings are at odds with a recent systematic analysis of competitive and recreational runners1. Alentorn-Geli et al. found that the overall prevalence of hip and knee osteoarthritis was 13.3% (95% confidence interval [CI], 11.6% to 15.2%) in competitive runners, 3.5% (95% CI, 3.4% to 3.6%) in recreational runners, and 10.2% (95% CI, 9.9% to 10.6%) in controls. The odds ratio of having osteoarthritis (hip and/or knee), relative to the controls, was higher in competitive runners (1.34 [95% CI, 0.97 to 1.86]) than in recreational runners (0.86 [95% CI, 0.69 to 1.07]). Different populations and arthritis definitions could cause the variance between the studies. The present study concentrates solely on marathoners, whereas the systematic analysis deals with recreational and competitive running. In both cases, to be successful, marathoners need to be healthy. As Kujala et al. have shown, high-level, active athletes have less cancer, fewer cardiac problems, and fewer respiratory issues than a comparable population2,3. The results of a cohort study of Finnish former elite athletes show that, compared with controls, in later life, athletes had less disability and better self-rated health and were less in need of hospital care. The disease risk reduction was highest in athletes who had participated in endurance sports. Similar data have been presented on cardiovascular health4. In Kujala’s studies, the only area in which active runners seem to have challenges is in the musculoskeletal area. The current study contradicts these findings in that active marathoners had lower arthritis prevalence than the comparable U.S. population. This contradiction may be caused by the arthritis definition and the fact that this was a self-reported survey. Additionally, the marathoners in this study were very experienced and may represent the principle of survival of the fittest. Runners with problems such as hip and knee pain have quit running marathons and, as such, the study is limited by selection bias.
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