TY - JOUR T1 - Increased risk of breast cancer associated with long-term shift work in Canada JF - Occupational and Environmental Medicine JO - Occup Environ Med SP - 831 LP - 838 DO - 10.1136/oemed-2013-101482 VL - 70 IS - 12 AU - Anne Grundy AU - Harriet Richardson AU - Igor Burstyn AU - Caroline Lohrisch AU - Sandip K SenGupta AU - Agnes S Lai AU - Derrick Lee AU - John J Spinelli AU - Kristan J Aronson Y1 - 2013/12/01 UR - http://oem.bmj.com/content/70/12/831.abstract N2 - Objectives Long-term night work has been suggested as a risk factor for breast cancer; however, additional studies with more comprehensive methods of exposure assessment to capture the diversity of shift patterns are needed. As well, few previous studies have considered the role of hormone receptor subtype. Methods Relationships between night shift work and breast cancer were examined among 1134 breast cancer cases and 1179 controls, frequency-matched by age in Vancouver, British Columbia, and Kingston, Ontario. Self-reported lifetime occupational histories were assessed for night shift work, and hormone receptor status obtained from tumour pathology records. Results With approximately one-third of cases and controls ever employed in night shift work, associations with duration demonstrated no relationship between either 0–14 or 15–29 years, while an association was apparent for ≥30 years (OR=2.21, 95% CI 1.14 to 4.31). This association with long-term night shift work is robust to alternative definitions of prolonged shift work, with similar results for both health and non-health care workers. Conclusions Long-term night shift work in a diverse mix of occupations is associated with increased breast cancer risk and not limited to nurses, as in most previous studies. ER -