Evidence of an effect of shift work on all-cause and cause-specific mortality is inconsistent. This study aimed to examine whether shift work is associated with increased all-cause and cause-specific mortality.Methods
We linked 28 731 females (age ≥44 years), recruited in 1993 or 1999 from the Danish nurse cohort with information on shift work (night, evening, rotating, day), to the Danish Register of Causes of Death to identify deaths until 2013. We used Cox regression models to examine associations between night, evening, and rotating shift work (compared to day) and all-cause and cause-specific mortality in models adjusted for confounding variables.Results
Of 18 015 nurses, 1616 died during study period from following causes: cardiovascular disease (CVD) (n=217), cancer (n=945), diabetes (n=20), Alzheimer’s or dementia (n=33) and psychiatric diseases (n=67). Working night [hazard ratio (HR) 1.26 95% confidence interval (95% CI) 1.05–1.51] or evening (HR 1.29 95% CI 1.11–1.49) shifts was associated with a significant increase in all-cause mortality when compared to day workers. We found a significant association of night shift work with CVD (HR 1.71 95% CI 1.09–2.69) and diabetes (HR 12.0 95% CI 3.17–45.2) and none with overall cancer mortality (HR 1.05 95% CI 0.81–1.35) or mortality from psychiatric diseases (HR 1.17 95% CI 0.47–2.92). Finally, we found strong association between evening (HR 4.28 95% CI 1.62–11.3) and rotating (HR 5.39 95% CI 2.35–12.3) shift work and mortality from Alzheimer’s and dementia.Conclusions
Women working night and evening shifts have increased all-cause, CVD, diabetes, and Alzheimer’s and dementia mortality.