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Circadian disruption has been linked to carcinogenesis in animal models, but the evidence in humans is inconclusive. Genetic variation in circadian rhythm genes provides a tool to investigate such associations. We examined associations of genetic variation in nine core circadian rhythm genes and six melatonin pathway genes with risk of colorectal, lung, ovarian and prostate cancers using data from the Genetic Associations and Mechanisms in Oncology (GAME-ON) network. The major results for prostate cancer were replicated in the Prostate, Lung, Colorectal and Ovarian (PLCO) cancer screening trial, and for colorectal cancer in the Genetics and Epidemiology of Colorectal Cancer Consortium (GECCO). The total number of cancer cases and controls was 15,838/18,159 for colorectal, 14,818/14,227 for prostate, 12,537/17,285 for lung and 4,369/9,123 for ovary. For each cancer site, we conducted gene-based and pathway-based analyses by applying the summary-based Adaptive Rank Truncated Product method (sARTP) on the summary association statistics for each SNP within the candidate gene regions. Aggregate genetic variation in circadian rhythm and melatonin pathways were significantly associated with the risk of prostate cancer in data combining GAME-ON and PLCO, after Bonferroni correction (ppathway < 0.00625). The two most significant genes were NPAS2 (pgene = 0.0062) and AANAT (pgene = 0.00078); the latter being significant after Bonferroni correction. For colorectal cancer, we observed a suggestive association with the circadian rhythm pathway in GAME-ON (ppathway = 0.021); this association was not confirmed in GECCO (ppathway = 0.76) or the combined data (ppathway = 0.17). No significant association was observed for ovarian and lung cancer. These findings support a potential role for circadian rhythm and melatonin pathways in prostate carcinogenesis. Further functional studies are needed to better understand the underlying biologic mechanisms.

Study objective There are some data to suggest that insufficient sleep, including short sleep duration and sleep disruption, may be associated with an increased risk of cancer. We investigated the association between sleep duration and sleep disruption and risk of prostate cancer. Design Prospective cohort study. Setting Sweden. Participants A total of 14,041 men in the Swedish National March Cohort. Interventions None. Measurements and results Habitual sleep duration and sleep disruption were self-reported in 1997. Prostate cancer diagnoses, including lethal (metastases at diagnosis or death from prostate cancer) and advanced (stage T4, N1, or M1 at diagnosis or death from prostate cancer), were determined from linkage to nationwide cancer registries through 2010. We conducted Cox proportional hazards regression adjusted for potential confounding variables. During 13 years of follow-up, we identified 785 cases of incident prostate cancer, including 118 lethal and 127 advanced cases. Four percent of men reported sleeping 5 h or less a night, and 2% reported sleeping 9 h or more per night. We found no association between sleep duration and risk of prostate cancer overall or for advanced/lethal disease. We also did not find an association between prostate cancer and sleep disruption, as defined by difficulty falling asleep, difficulty maintaining sleep, sleep quality, and restorative power of sleep. Conclusions In this large prospective study from Sweden, we found no association between habitual sleep duration or sleep disruption and risk of prostate cancer.