Sleep Duration and Prostate Cancer Risk in the Southern Community Cohort Study.

INTRODUCTION: The relationship between insufficient sleep and prostate cancer incidence is unclear. Our goal was to investigate the association of sleep duration, restless sleep, and prostate cancer incidence and aggressiveness, and whether race influences any sleep-prostate cancer association. METHODS: The Southern Community Cohort Study (SCCS) recruited study participants from 12 Southeastern states from 2002 to 2009. The cohort included nearly 35,000 males, predominantly African American (AA, 67%). Sleep exposures were measured via a baseline questionnaire at enrollment, which captured weekday and weekend sleep duration, weighted average sleep duration, and restless sleep. We used Cox proportional hazards models and multinomial logistic regression models to estimate associations between sleep and prostate cancer incidence and aggressiveness. RESULTS: During follow-up (median 10.9 years), 1345 men developed prostate cancer. Shorter sleep duration (< 6 h), in comparison to optimal duration (7-8 h), was suggestively associated with a decreased risk of prostate cancer in the overall cohort (adjusted hazard ratio (HR) = 0.83, (95% confidence interval (CI): 0.68-1.01) for sleep average; HR = 0.79, 95% CI: 0.65-0.95 for sleep weekdays; and HR = 0.81, 95% CI: 0.66-0.99 for sleep weekends), and among Black men (HR = 0.77, 95% CI: 0.62-0.97 for sleep average; HR = 0.76, 95% CI: 0.61-0.94 for sleep weekdays; and HR = 0.74, 95% CI: 0.59-0.94 for sleep weekends) when stratified by racial groups. Sleep duration and restless sleep were not associated with prostate cancer aggressiveness overall. CONCLUSION: Shorter sleep duration was suggestively associated with a decreased risk of prostate cancer, but sleep duration was not associated with aggressive prostate cancer. Stratified analysis suggests a reduction of prostate cancer risk among Non-Hispanic Black men with < 6 h of sleep, compared to those sleeping 7-8 h. This is an intriguing finding, and further research is needed to assess the impact of confounding factors on racial differences in prostate cancer development.