Physical activity, disability, and the risk of hospitalization for breast cancer among older women.

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Abstract
Background. A recent investigation of physical activity, disability, and the risk of breast cancer among older women in the Iowa 65+ Rural Health Study reported a decreased risk of breast cancer among women with any disability compared with physically capable but inactive women (relative risk [RR] = 0.4, 95% confidence interval [CI] 0.2–0.9). Because of the intriguing nature of that association, those investigators urged replication before drawing any conclusions. Methods. We replicated the Iowa approach using the Longitudinal Study on Aging (LSOA), a nationally representative, prospective cohort study. The 3131 community-dwelling women for whom we had complete data for these analyses ranged in age from 70 to 98 years old at baseline in 1984. Using ICD9-CM 174 codes, linked Medicare hospital claims identified 77 women with hospitalizations for breast cancer between 1984 and 1991. Multivariable proportional hazards regression was used to model the risk for this event among disabled, inactive, moderately active, and highly active women. Results. No significant association between disability in older women and the risk of hospitalization for breast cancer relative to inactive older women was detected (adjusted hazard ratio [AHR]-0.78, 95% CI 0.41–1.5). Highly active older women had a significantly reduced risk of hospitalization for breast cancer (AHR-0.42, 95% CI 0.19–0.95). Conclusion. The intriguing finding from the Iowa 65+ Rural Health Study that disabled older women's risk for breast cancer was reduced could not be replicated in the LSOA, although power was limited. Highly active older women, however, had a significantly lower risk for breast cancer in both studies.