Introduction
The medical profession is known for being difficult and hard, requiring tremendous effort from medical students. Beyond academic pressure, medical students grapple with challenges like peer competition, uncertain career prospects, and financial constraints ( Dyrbye, Thomas & Shanafelt, 2005 ; Nunez-Mulder, 2018 ). Such stressors may pose detrimental effects on the students’ health, particularly their mental well-being ( Dyrbye, Thomas & Shanafelt, 2006 ; Tosevski, Milovancevic & Gajic, 2010 ). Based on data from 167 cross-sectional and 16 longitudinal studies from 43 countries, Rotenstein et al. (2016) showed that the pooled prevalence of depressive symptoms among medical students was 27.2%, which was higher than that of non-medical school students ( Eisenberg et al., 2007 ; Steptoe et al., 2007 ). The available evidence indicates that medical students experience worse health status compared to the general population ( Dahlin, Joneborg & Runeson, 2005 ; Dyrbye, Thomas & Shanafelt, 2005 ). Self-rated health (SRH) is a measure that captures an individual’s evaluation of their general health condition, which has consistently demonstrated strong reliability, validity, and predictive power across various diseases and health conditions ( Lundberg & Manderbacka, 1996 ). As medical students are the future medical workforce, their health status is paramount. So far, previous studies have linked several adverse lifestyle factors, such as smoking, drinking, higher body mass index (BMI), and physical inactivity, which may contribute to the poor health status of medical students ( Liu et al., 2020 ; Mikolajczyk et al., 2008 ; Voltmer, Kotter & Spahn, 2012 ). However, more research is needed to identify other modifiable factors that may impact their suboptimal SRH.

Sleep is a critical health behavior central to human health. Sleep latency, the time it takes to fall asleep after going to bed, is an important indicator of sleep quality and reflects the degree of difficulty in falling asleep ( Halson et al., 2021 ; Siddiquee et al., 2023 ). Healthy individuals typically fall asleep within 10–20 min ( Jung et al., 2013 ). Studies have linked prolonged sleep latency to negative health outcomes, including poorer mental health, hypertension, and increased risk of mortality ( Joshi, 2022 ; Siddiquee et al., 2023 ; Zhong et al., 2022 ). However, most of these studies have focused on middle-aged and elderly populations ( Robbins et al., 2021 ; Siddiquee et al., 2023 ; Zhong et al., 2022 ). Medical students’ unique academic pressures and irregular work schedules make their sleep patterns and health status potentially different from that of the general population. Additionally, epidemiological data on sleep latency among young adults, particularly medical students, remains limited. To our knowledge, no studies have explored the association between sleep latency and suboptimal SRH in medical students. A systematic review suggests that cultural and ethnic factors may impact sleep patterns, including sleep latency ( Jeon, Dimitriou & Halstead, 2021 ). Moreover, previous studies have generally not considered important confounding such as sleep duration, chronotype, and nap habits, which are potential confounders that are closely related to sleep latency and SRH ( Baek, Jeong & Lee, 2024 ; Randler, Schredl & Göritz, 2017 ; Stefan et al., 2017 ; Walsh, Repa & Garland, 2022 ).

Given the above research limitations, our study aims to investigate whether sleep latency is associated with suboptimal SRH in Chinese medical students while accounting for confounders. We hypothesize that prolonged sleep latency is associated with an increased risk of suboptimal SRH and that this association may be moderated by lifestyle factors such as sleep duration, chronotype, afternoon nap, midnight snack habit, and BMI. Suboptimal SRH in medical students could inform targeted interventions to enhance their health outcomes. Additionally, these findings may offer epidemiological evidence to guide health assessment and management strategies for other high-stress occupational groups experiencing similar challenges.