Aim: Individual vulnerability to shift work disorder (SWD) varies. The aim of the present study was to verify the individual characteristics that predicted SWD onset by following Chinese intern nurses who at baseline had not worked rotating or night shifts.
Methods: A total of 706 Chinese first-year intern female nurses aged 16-24 years were recruited. At baseline (T0), they reported demographic characteristics, insomnia symptoms and excessive sleepiness, trait neuroticism, sleep reactivity, morningness, and circadian flexibility and languidity. At the three-month (T1) and six-month (T2) follow-up, the SWD status was determined based on significant sleep disturbance and/or excessive sleepiness in the context of working a rotating shift schedule.
Results and conclusions: The prevalence rates of SWD were 35.2% at T1 and 37.7% at T2. Two bivariate logistics regressions revealed that morningness (odds ratio [OR] = 1.31, 95% confidence interval [CI] = 1.09-1.58, T1; OR = 1.36, 95% CI = 1.12-1.65, T2), languidity (OR = 1.56, 95% CI = 1.28-1.90, T1), and sleep reactivity (OR = 1.29, 95% CI = 1.07-1.57, T1; OR = 1.31, 95% CI = 1.07-1.61, T2) predicted the onset of SWD, while flexibility (OR = 0.75, 95% CI = 0.62-0.90, T1) decreased the odds of SWD onset. By comparing nurses with SWD and nurses without SWD across all six months, morningness (OR = 1.58, 95% CI = 1.20-2.07), sleep reactivity (OR = 1.54, 95% CI = 1.16-2.04), languidity (OR = 1.70, 95% CI = 1.30-2.22), and flexibility (OR = 0.70, 95% CI = 0.54-0.90) showed significant effects on persistent SWD.
Keywords: Circadian rhythm; Shift work; Shift work disorder; Sleep reactivity.
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