Working hours, on-call shifts, and risk of occupational injuries among hospital physicians: A case-crossover study.

Objective: To investigate the association of hospital physicians' working hours and on-call shifts with the risk of occupational injuries.

Methods: In this nested cohort study of 556 Finnish hospital physicians, we linked electronic records from working-hour and on-call duty payroll data to occupational injury data obtained from the Finnish Workers' Compensation Center for the period 2005-2019. We used a case-crossover design with matched intervals for a 7-day 'case window' immediately prior to occupational injury and a 'control window' 7 days prior to the beginning of the case window, and analyzed their associations using conditional logistic regression models.

Results: We noted 556 occupational injuries, 281 at the workplace and 275 while commuting. Having three to four long (>12 h) work shifts on the preceding 7 days was associated with a higher probability of an occupational injury (odds ratio [OR] 2.14, 95% confidence interval [CI] 1.11, 4.09), and the OR for three to four on-call shifts was 3.54 (95%CI 2.11, 5.92) in comparison to having none of these work shift types. A higher number of several consecutive working days was associated with a higher probability of injury in a dose-response manner. Moreover, increasing weekly working hours was associated with an increased likelihood of injury (OR 1.03, 95%CI 1.01, 1.04), whereas the number of normal (≤12 h) work shifts reduced this likelihood (OR 0.79, 95%CI 0.64, 0.98).

Conclusions: Our findings suggest that accumulated working-hour load, as opposed to single, very long (>24 h) work shifts, may increase the risk of occupational injury among hospital physicians.