Cancer
The effects of working conditions on the risk of breast cancer: a cohort study Bernadette van der Linden* Bernadette van der Linden Joy Sudan Arnaud Chiolero Stéphane Cullati Salvatore Vaccarella Cristian Carmeli
Background Breast cancer is the most commonly diagnosed cancer among women worldwide. While unhealthy lifestyle behaviors have been established to increase the risk of breast cancer, the effect of working conditions is not well known. We aimed to quantify the effects of working-related physical activity and long working hours on breast cancer risk using a large-scale longitudinal cohort study.
Methods Data were from the UK Biobank and included 161,673 women between 40 and 69 years old without breast cancer at baseline (2006) and followed until the end of 2016. Exposures were heavy physical/manual work (yes, sometimes, no), walking/standing work (yes, sometimes, no), and working hours per week (<15, 16-30, 31-48, >49), all self-reported at baseline. Incident breast cancer diagnoses (outcome) were verified through linkage with cancer registries. We calculated the cumulative risk differences/ratios of breast cancer, standardized by age at baseline, attained education, history of illnesses and number of live births.
Results There were 5092 (3.1%) women diagnosed with breast cancer during the 9 years of follow-up. Heavy physical/manual work led to 680 (95% CI: 281 to 1054) fewer breast cancer cases per 100 000 women compared to no heavy physical/manual work. That corresponded to a risk ratio (RR) of 0.79 (95% CI: 0.67 to 0.95). Walking or standing work led to 325 (95% CI: 77 to 596) fewer breast cancer cases per 100 000 women compared to not walking or standing work (RR: 0.90; 95% CI: 0.79 to 0.98). Negligible differences in breast cancer risk were found for number of working hours.
Conclusion Heavy physical/manual and walking or standing work reduced breast cancer risk in women among the UK Biobank participants. This is in contrast to the known higher risk of cardiovascular diseases conferred by high levels of occupational physical activity. Further studies are needed to assess the transportability of these findings to other populations.