374 Night shift work and prolactin in nurses and midwives - preliminary results

Abstract

Objectives Night shift work and exposure to light at night suppress synthesis of melatonin and disrupt circadian rhythm. The pattern of secretion of many hormones, including prolactin, is dependent on circadian rhythm and prolactin has been found to play a role in breast cancer aetiology. So far, the data on the link between night shift work and prolactin are sparse. The aim of our study was to evaluate the association between rotating night shift work and prolactin concentration in nurses and midwives. Methods The cross-sectional study included 347 nurses and midwives currently working on rotating night shifts and 359 nurses and midwives working during the day. The prolactin concentration was measured in the morning blood samples using the ECLIA method. The associations were estimated by multiple linear regression models adjusted for: age, number of full-term births, current oral contraceptives use and time of blood collection. A potential modification by the menopausal status was analysed. Results No difference in the prolactin concentration was found between the women currently working on night shifts and the day nurses (geometric means (GM): 195.3 μU/ml vs. 194.7 μU/ml; p = 0.948). In women with 2 or more consecutive night shifts within one week before the blood collection, we observed a statistically significant increase of the prolactin concentration compared to the women who had only one night shift throughout that week (250.2 μU/ml vs. 216.9 μU/ml; p = 0.033). None of the examined associations were modified by the menopausal status. Conclusions The preliminary results of our study suggest that night shift work might modify prolactin secretion.