The study included 37,731 Dutch female nurses who reported on their sleep patterns and shift preferences over time.
Later are associated with a 55-minute later midsleep time compared to intermediate types.
Preferences for night and evening shifts increase with later chronotype, with odds ratios of 2.68 and 2.20, respectively.
Preferences for day and morning shifts decrease with later chronotype, with odds ratios of 0.17 and 0.22, respectively.
Intermediate chronotype is linked to fewer sleep problems, with a median score of 27.2 on the sleep problem index, compared to 28.9 for morning types and 31.7 for evening types.
Chronotype may influence sleep-wake times, shift type preference, and sleep issues among nurses.
Simplified
may affect tolerance for circadian disruption induced by shift work. This study examines the association between chronotype, self-reported sleep timing, shift type preference, and sleep problems among nurses, and studies chronotype stability over time. The study included 37,731 Dutch female nurses who completed a baseline (2011) and follow-up questionnaire (2017), with information on shift work (e.g., job history, shift type preference [collected in 2017 only]), and sleep characteristics (e.g., chronotype, preferred sleep-wake time in a work-free period [collected in 2017 only], and sleep problems between working days according to Medical Outcomes Study-Sleep Problem Index II []). The association between chronotype and sleep timing was examined using (age-adjusted) linear regression. Associations between chronotype and shift type preference and sleep problems (MOS-SPI-II >30) were examined using ordered logistic and Poisson regression, respectively. With later chronotype, midsleep time increased (definite evening vs. intermediate types [reference]: β = 55 min, 95% confidence interval [95% CI]: 54-55), the odds ratio (OR) for 1-point increase in preference for night (2.68; 95% CI: 2.48-2.90) and evening shifts increased (OR 2.20; 95% CI: 2.03-2.38), while the odds for day (OR 0.17; 95% CI: 0.16-0.18) and morning shifts (OR 0.22; 95% CI: 0.21-0.24) decreased. Intermediate chronotype was associated with fewer sleep problems (median MOS-SPI-II = 27.2, p < 0.01), compared with definite morning (28.9) and evening types (31.7). This study shows that chronotype is associated with sleep-wake times in a work-free period, shift type preference, and sleep problems in nurses. Future studies on the association of shift work-induced circadian disruption and health outcomes should therefore consider chronotype as effect-modifier.
Key numbers
55 min
Increase in Midsleep Time
Comparison of definite evening vs. intermediate types
2.20
Odds Ratio for Evening Shift Preference
Odds ratio comparing preference for evening shifts
27.2
Median Score
Median score for sleep problems in intermediate
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