Effects of Half- or Whole-Night Shifts on Physiological and Cognitive Parameters in Women

The study assessed the effects of whole- or half-night shifts on leptin, melatonin, sex hormones, interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), IL-6, hematological parameters, sleep quality and attentional performance in women working in the health sector.

Women working whole-night shifts (16:00-08:00 hours, n = 20), half-night shifts (16:00-24:00 hours, n = 20) or day shifts (08:00-16:00 hours, n = 20) participated in the study. Blood pressure, respiratory rate, proximal skin temperature (forehead), blood glucose, leptin, melatonin, estradiol, progesterone, IL-1β, TNF-α, and IL-6 concentrations, complete blood count and erythrocyte sedimentation rate (ESR) were measured in the beginning and at the end of the shifts. The participants filled in sleep quality questionnaires and performed visual attention tests.

Half- and whole-night shifts caused problems in sleep duration and quality and disturbed the melatonin rhythm. Women working both half- and whole-night shifts had significantly higher nucleated erythrocytes (P = 0.006), eosinophils (P = 0.031), lymphocytes (P = 0.001) and leptin concentrations (P = 0.001) but had lower ESR (P = 0.046) and neutrophil percentage (P = 0.001) than that of day-time workers. Whole-night shifts caused additional changes including lower attentional performance (P = 0.035), lower platelet counts (P = 0.000) and lower estradiol levels (P = 0.029), but higher TNF-α levels (P = 0.000), than the control group. Moreover, whole-night shifts increased IL-1β levels before the shift (P < 0.001) and increased IL-6 levels over the half-night shifts (P < 0.05).

Half-night shifts disturbed sleep parameters and the melatonin rhythm, perturbed blood cell turnover and increased leptin levels. Whole-night shifts caused additional problems including suppressed estradiol, activated inflammatory responses and decreased visual attention. All together, the data suggest that night shifts, especially whole-night shifts, should be refrained from or countermeasures should be taken.