The later, the better: Evening chronotypes in Uruguayan shift workers are associated with longer sleep in an observational study

Shift work disrupts sleep patterns and is linked to adverse health outcomes, yet the role of chronotype in modulating shift workers' sleep behavior remains underexplored. A field study was conducted with 85 shift workers from an industrial plant in Montevideo, Uruguay, operating under a slow, counterclockwise three-shift rotation system. The abbreviated Munich Chronotype Questionnaire was used to assess sleep timing, duration, and napping behavior across shifts, and chronotype. Sleep duration on workdays was significantly shorter during morning (4.9±0.8h) and night shifts (5.0±1.5h) compared to afternoon shifts (7.9±1.3h). Napping was more frequent during the morning (54.1%) and night shifts (52.9%), contributing to almost an additional hour of sleep to mitigate sleep debt. Evening-oriented workers demonstrated greater sleep flexibility and adaptability, sleeping longer on days off and during night and afternoon shifts: A 1-hour delay in chronotype associated with 7-25 minutes of additional sleep. Morning-oriented workers adapted better to advancing sleep during morning shifts and got more sleep. These results highlight the importance of considering individual chronotypes when designing shift schedules. Personalized shift schedules could enhance sleep health and mitigate the adverse effects of shift work.