Body mass index and rest-activity circadian rhythm in shift workers

The working hours of shift workers, which are scheduled outside the normal daily social program, lead to a circadian desynchronization due to a temporary misalignment between working hours and physiological and behavioral functions, similar to what is observed in Jet-Lag. This leads to a worsening of sleep, a reduction in the ability to work during waking hours and alertness. The aim of this study was to evaluate the effects of shift work on rest-activity circadian rhythm (RAR) in a sample of nurses, taking into account their body mass index (BMI). A total of 59 participants volunteered to be part of the study: 44 of them were night shift workers (Group1), 15 were daily workers (Group2). All participants were subjected to the following detections: height and weight, to calculate the BMI, and a continuous 7-day actigraphic monitoring to detect their activity levels. In order to evaluate RAR, we used the single cosinor method. A statistically significant RAR was found for all participants. Subsequently, we used the population mean cosinor to detect the presence of a significant circadian rhythm in Group 1 and 2. The results showed that amplitude referring to RAR resulted significantly different between the two groups, with lower values in Group1 compared to Group2 (p<0.001). In addition, we divided each group based on subject’s BMI (category A:<25 kg/m2; category B:≥25 kg/m2). The intra-group analysis didn’t show differences in amplitude for A and B. By contrast, the comparison between Group1 and Group2 for A and B showed an higher amplitude for Group2 compared to Group1 (A: p<0.003; B: p<0.004). It seems that the night shift is primarily involved in RAR alterations. In fact, night shift workers showed lower values of amplitude that could be associated with an higher risk for health problems.