The simultaneous exposure of shift workers to long shifts and short breaks has a synergistic interaction and increases the risk of depression, a new study shows.

Soon Chun Hyang University Hospital Seoul said Monday that a team led by Professor Lee June-hee of the Department of Occupational and Environmental Medicine analyzed data from 3,295 shift workers who participated in the sixth working environment survey conducted in 2020 and published a paper titled "Synergistic Interaction of Long Shift Work Hours and Short Rest Periods Between Shifts on Depression in Shift Workers."

Professors Park Sung-jin of the Department of Occupational and Environmental Medicine at Gangnam Giein Hospital and Lee Jong-in of the Department of Occupational and Environmental Medicine at Catholic University of Korea Seoul St. Mary's Hospital joined the team.

The researchers defined long shifts as working more than 10 hours per day on at least one occasion in the past month and short breaks as having less than 11 hours of rest between consecutive shifts on at least one occasion in the past month.

They defined a score of less than 50 points as depression using the World Health Organization Well-Being Index (WHO-5). They also estimated the association between the risk of depression and working short and long shifts through logistic regression.

The analysis showed that the prevalence of depression among shift workers was 32.9 percent. In the multivariate analysis, the risk of depression was not significantly associated with long shifts or short breaks, but exposure to both factors simultaneously significantly increased the risk of depression.

The relative excess risk from the interaction between the two factors also showed a statistically significant synergistic interaction for depression risk.

Sensitivity analyses stratified by occupation revealed a significant interaction in the combined white-collar and service occupation groups.

"It is not uncommon for shift workers to be exposed to long shifts and short breaks between shifts at the same time, which can increase job stress and interfere with physical recovery, adversely affecting their mood," Professor Lee June-hee said. "When planning shift schedules or establishing health policies for shift workers, care should be taken to avoid simultaneous exposure to both situations."

The paper, "Synergistic interaction between long shifts and short rest periods on depression in shift workers: A cross-sectional study from Korea," was published in the August issue of the American Journal of Industrial Medicine.