The Association of Sleep Trouble and Physical Inactivity with Breast Cancer Risk in Nova Scotia: Evidence from the Atlantic PATH Cohort

Breast cancer is a major public health concern, and modifiable health behaviors such as sleep quality and physical activity may influence risk. This study examined the associations between self-reported sleep trouble, sleep duration, and physical activity with breast cancer incidence in a prospective longitudinal cohort of 10,305 females from Nova Scotia. Breast cancer cases were identified through record linkage to the Nova Scotia Cancer Registry. Multivariable logistic regression models were used to estimate adjusted odds ratios (AORs) and 95% confidence intervals (CIs), accounting for sociodemographic factors, reproductive history, comorbidities, and other health behaviors. Frequent sleep trouble ("all of the time") was significantly associated with increased odds of breast cancer (AOR = 2.41, 95% CI = 1.09-5.34, <i>p</i> = 0.03), while no significant associations were observed between sleep duration and breast cancer risk. High physical activity was significantly associated with a lower risk of breast cancer (AOR = 0.58, 95% CI = 0.39-0.86, <i>p</i> < 0.01). These findings suggest that frequent sleep disturbances may be associated with an increased risk of breast cancer, while high physical activity appears to be linked to a lower risk of breast cancer. Further research is needed to explore these relationships and their underlying mechanisms.