Relationship between daytime napping duration and pan-cancer risk: a prospective cohort study based on the China Health and Retirement Longitudinal Study (CHARLS).

BACKGROUND: In recent years, cancer has become a hot topic in the field of health management, and its etiology may be related to a variety of factors. Current research suggests that daytime napping duration is associated with variety of diseases, but few studies have explored the relationship between daytime napping duration and the risk of pan-cancer. Therefore, we based our study on the CHARLS database and Mendelian Randomization (MR) to investigate the relationship between daytime napping duration and pan-cancer risk. METHODS: This study is based on the China Health and Retirement Longitudinal Study (CHARLS) and Mendelian Randomization (MR). We first used Mendelian Randomization to explore the causal relationship between daytime napping and pan-cancer. Cox proportional regression was used to investigate the relationship between daytime napping duration and the risk of pan-cancer. The RCS curve is used to display the non-linear relationship between daytime napping duration and pan-cancer risk. RESULTS: Among 6 166 Chinese participants, compared with those who never napped, the overall cancer risk decreased by 31.0% (HR = 0.690), 33.9% (HR = 0.661), and 41.4% (HR = 0.586) for individuals who napped 1-30 min, 31-60 min, and over 60 min, respectively. Restricted cubic splines indicated a linear inverse association between nap duration and cancer risk (P for non-linear = 0.552), and sensitivity analyses yielded consistent results. CONCLUSION: Longer daytime napping duration was associated with a lower overall cancer risk. After adjusting for multiple confounders, people who napping over 60 min remained linked to an approximately 40% reduction in cancer risk. Our study found an inverse association between daytime napping duration and cancer risk, but larger sample sizes and objective sleep measurements are still needed for validation.