Night shift work and sickness absence – many for the few or few for the many?

BACKGROUND: Night shift work is related to adverse health outcomes. Yet, some choose working permanent night and it is speculated that they tolerate night work better. However, research on permanent night work is sparse. The aim was to study the association between organisation of night work and sickness absence. Should we allow many night shifts for the few or should we enforce few night shifts for the many? METHODS: Information on working hours, age (19-70 years), gender (women, men) and sickness absence (annual number of days) was obtained from 94 815 nurses and nurse assistants (88% women) from the Danish Working Hour Database (DAD). DAD contains daily information on working hours based on payroll data for all employees in Danish public hospitals (2017-2020). For each year with >50% work participation, individual schedules were classified into “no night shifts”, “1-50 night shifts”, “51-100 night shifts”, “101-150 night shifts” and “more than 150 night shifts”. We applied linear regression (with individual as random intercept) for risk of sickness absence the following year adjusted for age, gender and calendar year. RESULTS: Preliminary results showed night shift workers with more than 150 night shifts per year had 5.0 more sick days (95% CI: 3.5-6.4, p = <0.001) than employees with no night shifts. No statistically significant differences were observed between the four night shift groups. CONCLUSIONS: Employees had more sickness absence the year after working during the night compared to employees without night shift work. However, no differences were seen when yearly comparing employees with many night shifts to those with few night shifts. The study adds to scientific support to guidelines on scheduling of shift work in governmental policies with the aim of securing healthy and safe workplaces. KEY MESSAGES: • Night shift workers have higher number of sick days compared to daytime workers; however, number of night shifts during a year did not affect the results. • The study adds value for the use of the scientific recommendations for minimizing health risk for night shift workers in governmental policies with the aim of securing healthy and safe workplaces.