Bimodal chronotype in night-shift workers

Introduction. Typology of diurnal (circadian) human rhythms is actively studied in occupational medicine, from the viewpoint of adaptation to various work conditions including those with shift working schedule. In recent years, evidences outline bimodal chronotype characterized by simultaneously present signs of extreme morning and extreme evening types without dominating one of them. Studies did not cover bimodal chronotype in night-shift workers.Objective is to evaluate presence of bimodal chronotype in night-shift workers if compared to day-shift schedule.Materials and methods. Chronotype outlining covered 95 workers divided into 2 groups: first — 55 night-shift workers, second — 40 workers on day schedule. Bimodal chronotype was diagnosed via algorithm based on questionnaire Morningness Eveningness Questionnaire (MEQ) by B.J. Martynhak et al.Results. Findings are that 7.3% of night-shift workers and 5.0% of workers with day schedule demonstrate bimodal chronotype. Changed chronotype classification leads to smaller share of workers with intermediate chronotype, but quota of morning and evening chronotypes does not change. Possibility of bimodal chronotype should be respected in examination of workers for designing health programs with consideration of chronotype-associated diseases and for better performance due to rational management of working time.Conclusions. Diagnosis of individual chronotype is a serious part in health programs formation in able-bodied population. Chronotype knowledge helps to minimize possible decrease and losses of performance due to rational working time management and preventive programs aimed to diagnose chronotype-associated health disorders.