[Night work and health of nurses and midviwes--a review]

Night shift work has been thought to play a role in the etiology of chronic diseases through a disruption of the circadian rhythm, decreased synthesis of melatonin and sleep deprivation. Our aim was to review the epidemiological studies on the association between night shift work and some pathologies in nurses and midwives. We reviewed publications available in the MEDLINE database and published before June 2012, describing the cross-sectional (almost two thirds of all papers) and cohort studies. In total, we identified 26 original papers, including 5 epidemiological studies addressing diseases or disorders of the digestive system, 3--metabolic syndrome, 2--type 2 diabetes, 9--cardiovascular diseases and (CVD risk factors, 5--obesity/overweight, 2--menstrual disorders and 3--poor pregnancy outcomes. The analysis of the literature indicates that night shift work of nurses and midwives is most strongly associated with a higher risk ofobesity/overweight. In each of the five studies, which we identified this association was observed (confirmed by the statistical significance of the results), also after adjustment for confounders. The results for type 2 diabetes and disorders of the menstrual cycle are also suggestive. Epidemiological data on the other disorders or pathologies discussed in this article seem to be less certain - their results are inconsistent or their number is too small to draw definite conclusions. Further epidemiological studies of nurses and midwives working on night shifts and prospective observations in particular are recommended to find out whether potential association between the night work and discussed health issues is causal.