reduced disability and mortality among aging runners
as much as i love to run, i'm skeptical about the health claims made in magazine's such as runner's world. in my opinion, most of the studies don't even begin to address the basic self-selection problems in comparing runners with non-runners. a new stanford study of older runners ranks among the best i've seen, applying a basic covariate adjustment strategy (statistically controlling for the effects of age, sex, body mass index, smoking, and initial disability level) to some high-quality longitudinal data.
eliza chakravarty, helen hubert, vijaya lingala, james fries are authors of "reduced disability and mortality among aging runners" in the latest issue of the archives of internal medicine. in my view, this study helps answer the practical question of whether the health benefits of running outweigh any negative health impacts of pounding the pavement. from the abstract:
Annual self-administered questionnaires were sent to 538 members of a nationwide running club and 423 healthy controls from northern California who were 50 years and older beginning in 1984. Data included running and exercise frequency, body mass index, and disability assessed by the Health Assessment Questionnaire Disability Index (HAQ-DI; scored from 0 [no difficulty] to 3 [unable to perform]) through 2005. A total of 284 runners and 156 controls completed the 21-year follow-up. Causes of death through 2003 were ascertained using the National Death Index. Multivariate regression techniques compared groups on disability and mortality. At baseline, runners were younger, leaner, and less likely to smoke compared with controls. The mean (SD) HAQ-DI score was higher for controls than for runners at all time points and increased with age in both groups, but to a lesser degree in runners (0.17 [0.34]) than in controls (0.36 [0.55]) (P < .001). Multivariate analyses showed that runners had a significantly lower risk of an HAQ-DI score of 0.5 (hazard ratio, 0.62; 95% confidence interval, 0.46-0.84). At 19 years, 15% of runners had died compared with 34% of controls. After adjustment for covariates, runners demonstrated a survival benefit (hazard ratio, 0.61; 95% confidence interval, 0.45-0.82). Disability and survival curves continued to diverge between groups after the 21-year follow-up as participants approached their ninth decade of life.
here's is the survival distribution of runners and the comparison group over the study's 21 years (cut and pasted from the original):
the following figure shows predicted disability from linear mixed models, net of the covariates mentioned above.
the upshot is that runners tend to live longer and avoid disability, relative to a non-running comparison group, and that the differences persist into later life. the authors are appropriately cautious in drawing causal inferences, but the results convince me that i should keep running -- and that, on average, the benefits of running outweigh any potential negative effects (e.g., on battered joints or burned-up skin or exploding hearts).