Short-term effects of night shift work on breast cancer risk: a cohort study of payroll data

Night-shift work and breast and prostate cancer risk: updating the evidence from epidemiological studies

“…In spite of this apparent consensus regarding the association between nightshift work and breast cancer risk, there were other studies that found no relati-oship 34,38,41,42,54,57 . Some authors point out that this could possibly be due to the relevance of menopausal status as a determining factor and the number of pre-menopausal and post-menopausal women in the sample population.…”

“…The pre/ post-menopausal status of female participants should also be considered since this is another important risk factor for breast cancer, as postmenopausal women can be more exposed to hormones through oestrogen replacement therapy, in addition to their increased age 83 . Other limitation of our review was that the sample population in many studies on shift work and breast cancer risk consisted solely of nurses; the majority of these studies, exception made by the more recent ones 34,54 , reported a higher risk of breast cancer in women working on night-shifts for long periods. However, this association might be affected by confounding factors, such as alcohol and smoking habits, previously mentioned.…”

“…This systematic review included thirty-three studies that assessed the association between night-shift work and breast or prostate cancer. All the included studies found that there was a positive association between circadian disruption and cancer, although in some of them the association was non-significant, either for breast [33][34][35]38,41,42,44,47,[54][55][56][57]63,65 or for prostate cancer [50][51][52][53]56,59 . According to NOS, the included studies had low risk of bias, given that 90.3% of them scored more than seven stars.…”

Shift work and cardiovascular disease – do the new studies add to our knowledge?

“…For the other eight risk of bias parameters, all five studies were assessed as being equal. This actually questions the reliability of the reported 7.1% increasing relative risk per five years of shift work, which may be affected by recall bias and stresses the need for analyses based on objective exposure as well as objective outcome data (23,24).…”

Response to Dr Stevens’ letter ref. Visitisen et al: “Short-term effects of night shift work on breast cancer risk: a cohort study of payroll data”

“…We thank Dr Richard Stevens for his comments (1) on our recent article that showed no increased risk of breast cancer following recent night shift work when compared with recent day shift work (2). This finding was based on linkage of day-by-day information on working hours and breast cancer incidence data.…”