The association of sleep duration and quality with obesity-related cancers: Results from the health examinees study

This study aims to investigate the associations of self-reported sleep duration and quality with obesity-related cancer risk in a large-scale Korean population. This prospective cohort study utilized data from the Health Examinees-Gem (HEXA-G) cohort, comprising adults aged ≥40 years. A total of 126,866 participants who provided information on both sleep duration and quality were included in the present study. Sleep duration was self-reported at baseline and categorized into <6 hours, 6-<8 hours, and ≥8 hours. Sleep quality was assessed using four independent questions, including nonrestorative sleep, daytime fatigue, difficulty in initiating sleep, and nighttime anxiety. Cancer cases were identified through national cancer registration data from the Korea Central Cancer Registry of the Korea National Cancer Center. This study adopted obesity-related cancers, defined by the International Agency for Research on Cancer. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), with follow-up beginning two years after the age at enrollment and continuing until the first cancer diagnosis, loss to follow-up, or the end of the study (December 31, 2018). During the median follow-up period of 7.3 years (range, years), 7,284 incident all-site cancer cases, including 4,113 obesity-related cancer cases, were documented. Long sleep duration (≥8 h) was significantly associated with obesity-related cancer (1.08; 1.01-1.16), marginally associated with all-site cancer (1.05; 1.00-1.11), and not associated with non-obesity-related cancer. Compared with participants reporting each sleep quality component “not at all,” those reporting nonrestorative sleep “sometimes” (1.08; 1.01-1.16) or “most of the time” (1.11; 1.01-1.22) showed higher obesity-related cancer risk; those reporting initiation difficulty “sometimes” was associated with obesity-related cancer risk (1.08; 1.01-1.16), whereas daytime fatigue and nighttime anxiety showed no significant associations. Reporting sleep ≥8 h with nonrestorative sleep (“sometimes”) increased all-site cancer (1.10; 1.01-1.20) and obesity-related cancer risk (1.24; 1.11-1.39). Reporting sleep ≥8 h with daytime fatigue increased all-site cancer (1.18; 1.06-1.31) and obesity-related cancer risk (1.19; 1.04-1.37). Reporting sleep ≥8 h with initiation difficulty increased all-site cancer (1.16; 1.04-1.30) and obesity-related cancer risk (1.26; 1.13-1.41). Long sleep duration was significantly associated with obesity-related cancer risk. Long sleep duration combined with nonrestorative sleep, daytime fatigue, initiation difficulties, or nighttime anxiety had positive associations with all-site and obesity-related cancer risks, but not with non-obesity-related cancers.