The vulnerability of individual employees to work schedules with night shifts

Introduction. 15-20% of the working population is engaged in various degrees of night work, which is a risk factor for many chronic diseases. The most significant causes are the duration, frequency, and degree of disruption of the daily rhythm — the length of shift work, the frequency of night shifts, the possibility of short sleep (napping) in the night shift. The age, gender, and chronotype of the employee are most often considered as indicators of vulnerability to night work (VNW), but the effectiveness of using these individual characteristics in predictive models of disease risk during shift work remains unclear.

The aim of the study is to use the proposed indicator of VNW to investigate its dependence on age, length of shift work, gender, chronic fatigue, health status, labor intensity and working environment conditions.

Material and methods. Two indicators were used: usual fatigue of the employee more when working in the night shift than when working in the day shift (VNW. 1); great fatigue from evening and night work (VNW. 2). The following groups were Studied: 1 group GR1-688 employees of continuous production enterprises and health organizations that use working modes with night shifts; GR2-298 employees of an oil refinery; GR3-679 employees of education and health care; GR4-630 University teachers. Employees were asked about their health status, symptoms of chronic fatigue and its professional and non-professional factors and working conditions. The level of labor intensity of GR1 and GR2 employees was assessed. Was used the annual increase in risk indicator (AIR) to study the age’s and experience’s dynamics of health status (AIR_ag and AIR_ex). Was used data on diseases detected during the medical examination of employees of GR1 and GR4.

Results. In the first year of shift experience, 50-55% of employees in groups GR1 and GR2 are tired during the night shift, more than during the day. With 2 years of experience, such workers become about 2 times less, then within 10 years the risk of VNW. 1 gradually increases to a level close to the value in the first year of service. Employees of GR1 and GR2 were not found to have any dependence of VNW. 1 from the age range of 25-64 years. In GR4, the V-inverse relationship of VNW. 2 is established from the age. With the same professions at oil refinery VNW. 1 is more often observed in women ((RR=1.17;0.49-2.8). For different health indicators the ratio of AIR_ex/AIR_ag amounted from 2.4 to 5.0. In GR1 at VNW. 1 an increased risk of chronic infectious diseases has been identified (RR=13.6; 1.67-111.0) and onychomycosis (women — RR=2.45 (2.023.00); men RR=1.49 (0.96-2.30). The V-shaped dependence of the risk of VNW. 1 is established. 1 on the intensity of labor.

Conclusions. When working with night shifts, 30-50% of employees are more tired when performing the same work at day shift. These workers do not adapt to night shifts. When working with night shifts, the risk of various chronic health disorders is 2.4-5 times greater than their age trend. Long-term VNW. 1 is one of the signs of the development of chronic fatigue and deterioration of the overall health of the employee. The employee's risk of VNW increases when exposed to a variety of professional and non-professional chronic stressors.

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