Night work and cancer risk: results from the ELSA-Brasil worker cohort.

OBJECTIVE: To estimate the association between exposure to night work and the incidence of breast, prostate, and colorectal cancer among participants in the Estudo Longitudinal de Saúde do Adulto (ELSA-Brasil - Longitudinal Study of Adult Health). METHODS: ELSA-Brasil is a multicenter cohort study conducted in the Northeast, South, and Southeast regions of Brazil. A total of 14,787 participants were included at baseline (2008-2010) and followed through 2023, with a mean follow-up duration of 13 years (SD = 2.22). Exposure to night work was defined based on self-reported occupational history, considering cumulative duration. Incidence cases of cancer were identified during follow-up. Associations were estimated using Cox regression models, adjusted for sociodemographic, behavioral, and occupational variables. RESULTS: Exposure to night work for more than ten years was associated with an increased risk of prostate cancer (HR = 1.38; 95% CI 1.09-1.75) and colorectal cancer (HR = 1.35; 95% CI 1.09-1.68), compared with exposure to day work. No association was observed between breast cancer and night work (HR = 0.89; 95% CI 0.65-1.22). CONCLUSION: The results suggest that prolonged exposure to night work may increase the risk of cancer, particularly prostate and colorectal cancer. This is the first study from the ELSA-Brasil cohort to analyze cancer incidence, expanding knowledge on work-related cancer and reinforcing the carcinogenic potential of night work, with implications for occupational health surveillance and cancer prevention policies in public health.