DISTURBANCES IN HORMONAL PROFILES OF NIGHT WORKERS DURING THEIR USUALSLEEP AND WORK TIMES

In a previous study, the authors reported that the 24-h rhythms of pit uitary and adrenal hormones-that is, thyrotropin (TSH), prolactin (PRL ), growth hormone, and cortisol-adapted only partially in a group of p ermanent night workers. However, the real impact of circadian rhythm a lterations on the health and well-being of subjects is still unclear. In this study, the authors focus on an ergonomic field and address que stions of adaptation of these hormones during the usual day sleep time (0700-1500 h) and during the usual night work time (2200-0600 h) in p ermanent night workers. Eleven night workers, working a night schedule for at least 2 years, submitted to a high-frequency blood sampling pr ocedure (10 min) and to electroencephalographic recordings during slee p. The endocrine profiles of night workers were compared to those of d ay-active subjects studied during their usual sleep-wake schedule. Dur ing usual day sleep, despite an adapted sleep structure, cortisol leve ls among night workers were abnormally enhanced, whereas the TSH decre ased in comparison to the plateau observed among day-active subjects. During usual work time, some hormonal disturbances persisted, in parti cular concerning cortisol and PRL (two hormones known to reflect the l evel of activation). Among night workers, the work time was associated with the quiescent period of cortisol secretion normally occurring du ring the first hours of sleep, and with a transient PRL increase. Thes e results revealed altered hormonal profiles during the sleep time of night workers that do not result in an altered sleep pattern. The noct urnal work time, which requires a high level physical and mental perfo rmance, is associated with some endocrine alterations reflecting an ev entual phase of hypovigilance.