The effects of the chronotype-shift type interaction and social jetlag on sleepiness, sleep quality, and burnout in shift workers

This study investigated how chronotype dimensions, shift-specific social jetlag, personality traits, and demographic factors relate to sleepiness, sleep problems, and burnout in shift workers. Participants were 200 blue-collar employees in the automotive sector (53.5% women; mean age = 34.72 ± 6.80 years; total work experience = 13.37 ± 5.82 years; tenure at the current workplace = 10.08 ± 5.00 years). Using a within-subject repeated-measures design, assessments were conducted during night, evening, and morning shifts. Linear mixed-effects models with a first-order autoregressive covariance structure showed significant shift type × morningness interactions across all outcomes (F = 3.80–29.58, p ≤ 0.05) and significant shift type × eveningness interactions across all outcomes (F = 9.60–23.13, all p < 0.001). Shift-specific social jetlag was positively associated with sleepiness (B = 0.308, p = 0.001), difficulty falling asleep (B = 0.186, p = 0.006), difficulty waking up (B = 0.153, p = 0.003), and work-related and personal burnout (B = 0.049, p = 0.013), but not with work environment-related burnout. Higher morningness predicted poorer night-shift adaptation, whereas higher eveningness was associated with fewer adverse outcomes. These findings support chronotype-sensitive scheduling and interventions targeting shift-specific social jetlag.