Night shift work characteristics and 6-sulfatoxymelatonin (MT6s) in rotating night shift nurses and midwives

Abstract

Objectives Synthesis of melatonin follows a circadian cycle, with high melatonin levels during the night and low levels during the day. Light exposure at night has been hypothesised as one of potential mechanisms of breast carcinogenesis in the night shift workers through inhibition of melatonin synthesis. The aim of the study was to examine a number of determinants for night shift work in relation to 6-sulfatoxymelatonin (MT6s), primary melatonin metabolite. Methods The cross-sectional study included 354 nurses and midwives (aged 40e60 years) currently working on rotating night shifts and 370 working days only. Data from questionnaires and 1-week diaries were used to characterise current job and total occupational history. Associations between rotating night shift work characteristics and MT6s (creatinine adjusted) in spot morning urine were tested in multiple linear regression models.Results No significant differences were found for MT6s concentrations between women currently working on rotating night shifts and those working only day shifts (means 47.2 vs 45.7 ng/mg Cr, respectively). The adjusted means among rotating night shift nurses and midwives varied depending on the department of employment, from 35.1 ng/mg Cr in neonatology to 68.2 ng/mg Cr in the orthopaedics department. Women working eight or more night shifts per month had significantly lower MT6s levels than those having fewer night shifts per month (37.9 vs 47.4 ng/mg Cr, respectively). Total night shift work history was not associated with MT6s. Conclusions The results of this study indicate that working eight or more night shifts per month may disrupt the synthesis of melatonin.

Night shift work and other determinants of estradiol, testosterone, and dehydroepiandrosterone sulfate among middle-aged nurses and midwives

“…This cross-sectional study was described elsewhere (28). Carried out between 2008-2011, the study included nurses and midwives, aged 40-60 years, who were currently employed in public healthcare in Lodz, Poland.…”

“…In spot morning urine samples, a biomarker of melatonin [ie, 6-sulfatoxymelatonin (creatinine adjusted)] was measured as described in our previous paper (28).…”

Circadian gene expression in peripheral blood leukocytes of rotating night shift nurses

“…A cross-sectional study of 354 nurses and midwives, all female, currently working rotating night shifts and 370 nurses who work only during the day was carried out in Lodz, Poland in 2008-2011 (23). Women were selected from the Local Registry of the Chamber of Nurses and Midwives.…”

“…However, disturbances of these cycles by irregular sleep hours, shift work, or light at night exposure may induce alteration of the SCN and peripheral circadian rhythms. Therefore, the aim of our analysis, which forms part of a cross-sectional epidemiological study of nurses and midwives (23), was to determine the effect of rotating night shift work on the expression of selected core circadian genes: BMAL1, CLOCK (positive regulators), CRY1, CRY2, PER1, PER2, and PER3 (negative regulators) as indicators of peripheral clock.…”

Night shift work and modifiable lifestyle factors

“…Night shift work might have an impact on personal life, in particular social and family life [12]. Moreover, unhealthy lifestyle changes have been suggested as contributors in the etiology of potential health effects of shift work [13] and the evidence for the association between night shift work and lifestyle factors, like smoking [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], alcohol consumption [15,17,18,20,24,27,[29][30][31][32], physical activity [21,25,27,29,33] and dietary habits [34] has been mounting. Nevertheless, epidemiological data on this subject are so far relatively sparse and inconclusive.…”