Independent and joint effects of sleep duration and sleep quality on suboptimal self-rated health in medical students: A cross-sectional study

OBJECTIVE: Studies on the association between sleep behavior and health often ignored the confounding effects of biorhythm-related factors. This study aims to explore the independent and joint effects of sleep duration and sleep quality on suboptimal self-rated health (SRH) in medical students. METHODS: Cross-sectional study. Proportional stratified cluster sampling was used to randomly recruit students from various medical specialties at a medical university in eastern China. Our questionnaire mainly included information on basic demographic characteristics, SRH, sleep behavior, and biorhythm-related factors. The independent and joint effects of sleep duration and sleep quality on suboptimal SRH were assessed by logistic regression after controlling for potential confounders. RESULTS: Of 1,524 medical students (mean age = 19.9 years, SD = 1.2 years; 59.1% female), 652 (42.8%) had suboptimal SRH. Most medical students (51.5%) slept for 7 h/night, followed by ≥8 (29.1%) and ≤ 6 h (19.4%). After adjusting for basic demographic characteristics and biorhythm-related factors, compared with students who slept for ≥8 h/night, the adjusted ORs (95%CI) for those who slept 7 and ≤ 6 h/night were 1.36 (1.03, 1.81) and 2.28 (1.60, 3.26), respectively (P < 0.001 for trend); compared with those who had good sleep quality, the adjusted ORs (95%CI) for those who had fair and poor sleep quality were 4.12 (3.11, 5.45) and 11.60 (6.57, 20.46), respectively (P < 0.001 for trend). Further, compared with those who slept for ≥8 h/night and good sleep quality, those who slept ≤ 6 h and poor sleep quality had the highest odds of suboptimal SRH (OR 24.25, 95%CI 8.73, 67.34). CONCLUSIONS: Short sleep and poor sleep quality were independently and jointly associated with higher odds of suboptimal SRH among medical students.