Chronotype differences in the risk of cancers, diabetes mellitus, and poor mental health among shift workers: a meta-analysis

OBJECTIVE: Shift work is associated with various leading causes of premature death, which has been linked with individuals with specific chronotypes. This study synthesized evidence on chronotype's role in associations between ever shift work and health outcomes. METHODS: Six databases were searched (inception-September 2025) for cohort/case-control studies assessing chronotype-specific shift work impacts on breast/prostate cancer, diabetes mellitus, and mental health. PRISMA guidelines were used for reporting. RESULTS: Fourteen studies were included in the review, comprising 2247 breast cancer cases, 3045 prostate cancer cases, 336 218 participants in diabetes studies, and 2128 poor mental health cases. Compared to daytime workers, both night shift workers with morning or evening chronotypes were more susceptible to breast cancer [morning type: pooled odds ratio (OR) 1.54, 95% confidence interval (CI) 1.01-2.37; evening type: pooled OR 1.41, 95% CI 1.04-1.90) and poor mental health (morning type: pooled OR 1.19, 95% CI 1.12-1.27; evening type: pooled OR 1.11, 95% CI 1.05-1.17]. Notably, night shift workers with evening chronotype were 84% more likely to develop prostate cancer than daytime workers. A positive dose-response relationship was identified between cumulative years of night shifts and prostate cancer among night shift workers with evening chronotype, indicating a 2.1% increase in risk for each additional year (P=0.012). CONCLUSIONS: Chronotype-matched scheduling does not effectively mitigate night shift risks. Nevertheless, evening chronotype night shift workers are particularly susceptible to various chronic non-communicable diseases, with a notable positive dose-response relationship observed between prostate cancer and evening chronotype night shift workers.