Abstract B145: Association between physical activity, sleep duration, and cancer risk among women in Washington County, MD: A prospective cohort study

Physical activity is known to be protective for multiple cancers including breast. Modulation of hormonal factors such as leptin, ghrelin, and hyperinsulinemia as well as energy balance and BMI are thought to play a protective role. Short duration of sleep appears to have an opposite effect on many of these factors.

In a population based prospective cohort (CLUE II), we assessed the association between physical activity energy expenditure (PAEE), sleep duration, and incidence of first cancer (all-site) in women. 5968 adult females who answered questions on sleep and physical activity on a 1998 follow up questionnaire were included in the study population. Incident cases were identified through linkage of cohort participants with the Washington County Cancer Registry and Maryland State Cancer Registry. Adjusted hazard ratios (HR) and 95% confidence intervals were estimated from Cox proportional hazards models. All statistical tests were two sided.

During 9.6 years of follow up, 604 1^st incident cancer cases including 186 breast cancers were diagnosed. Overall cancer risk (HR=0.80, 95% CI 0.68, 0.95) and breast cancer risk (HR=0.75, 95% CI 0.55, 1.01) were significantly reduced among women in the upper 50% of PAEE compared to the lower. Sleep duration was not significantly associated with overall or breast cancer risk in adjusted HR models, but with an increase in colon cancer risk (HR = 1.72, 95% CI 0.99, 2.78) though the sample size was small. Excluding elderly women (> 65 yrs in 1998) who may have different sleep patterns, sleep duration [≥ 7hrs/day vs. < 7hrs/day] significantly modified the association between PAEE [upper vs. lower 50%] and overall cancer risk (p interaction=0.014). A 1.5 fold increase in cancer risk (HR=1.47, 95% CI 1.05, 2.06) was observed among women ≤ 65 years in the upper 50% of PAEE who did not have sufficient sleep (< 7 hrs/day).

Increased PAEE was protective for cancer risk irrespective of age. In addition insufficient sleep may modify the observed protective effect of increased PAEE on cancer incidence among young and middle aged women.

Citation Information: Cancer Prev Res 2008;1(7 Suppl):B145.