Grant: Master's Award: Canada Graduate Scholarships

Breast cancer is the leading cause of cancer in Canadian women. Strong evidence has linked long-term shiftwork to breast cancer, but there remains uncertainty regarding the underlying mechanisms. In the healthcare industry, where shiftwork is necessary and the prevalence of this type of work is high, over 80% of workers are female. As such, female hospital workers represent an at-risk population for circadian-induced breast cancer. Many studies have examined melatonin patterns as a biomarker for circadian disruption, although few have considered exactly how circadian disruption is linked to breast cancer. A potential pathway between circadian disruption and breast cancer is circadian gene methylation. The scant research on this pathway has neglected specific aspects of shiftwork such as intensity, duration, and frequency, leading to exposure misclassification. Despite the evidence that both shiftwork and breast cancer risk are associated with melatonin disruption, there has been no study that considers the interaction between melatonin and circadian gene methylation. Using data collected in a new cross-sectional study (funded by the Cancer Research Society) at the Kingston Health Sciences Center, this study aims to examine two relationships: 1) sleep patterns and melatonin levels; and 2) melatonin levels and circadian gene methylation. Data collected from pre-menopausal female hospital employees will also consider current shiftwork status, detailed lifetime shiftwork parameters, and shift intensity. This study will provide epigenetic insight into early breast cancer development in hopes of informing future large-scale studies and providing evidence for workplace policy decisions including considerations of breast cancer prevention.