PURPOSE: Sleep timing and regularity are associated with various health and performance outcomes, but limited research has investigated the relationship of these sleep dimensions with cancer incidence. The objective of this study was to investigate the associations of sleep midpoint and social jetlag with cancer risk among US adults.
METHODS: The Cancer Prevention Study-3 is a large prospective study of US adults aged 30-65 years. At the first triennial follow-up (2015), participants were asked to report the average time they spent sleeping during a 24-h weekday and weekend, respectively. Sleep midpoint was calculated as the wake time minus half of sleep duration on a weekday and weekend to create a 5:2 weekday:weekend weighted average which was categorized as < 2:30AM, 2:30- < 3:30AM (referent), and ≥ 3:30AM. Social jetlag measures were calculated to estimate the difference in sleep midpoint on the weekend and weekday and categorized as < 1 h (referent), 1- < 2 h, and ≥ 2 h. Cancer incidence was determined via linkage to state registries; follow-up time ended at the time of cancer diagnosis or death or end of follow-up (12/31/2020). We used multivariable Cox proportional hazards models to estimate adjusted hazard ratios and 95% confidence intervals adjusted for socio-demographics, socioeconomic status, comorbidities, and lifestyle behaviors.
RESULTS: A total of 5,537 incident cancer cases were reported among 145,386 CPS-3 participants. We found no statistically significant associations of sleep midpoint or measures of social jetlag with overall cancer or breast cancer-specific risk.
CONCLUSION: Our findings suggest no significant associations of sleep midpoint and social jetlag with cancer risk.
