Insomnia and Its Impact on Psychomotor Reactivity, Autonomic Function, and Psychological Well-Being Among Medical Students: A Cross-Sectional Analytical Study.

Background Insomnia is a common sleep disorder associated with impaired cognitive function, psychological distress, and adverse health outcomes. Medical students, owing to their demanding academic schedules and lifestyle patterns, are particularly vulnerable to sleep disturbances. This study aimed to determine the prevalence and severity of insomnia among medical students and to explore its associations with cardiac autonomic status, psychomotor vigilance, psychological well-being, and body composition. Methods In this cross-sectional analytical study, a total of 118 second-, third-, and final-year MBBS students were recruited using stratified cluster random sampling. Insomnia severity was assessed using the Insomnia Severity Index (ISI). Psychological well-being was evaluated with the Depression, Anxiety, and Stress Scale (DASS-21). Auditory and visual reaction times (RTs) were measured using the RTM-608 Response Analyzer. Short-term heart rate variability (HRV) was analyzed using a 5-minute ECG recording. Anthropometric measures and body composition were assessed using standardized protocols and bioelectrical impedance analysis. Data were analyzed using appropriate parametric and non-parametric tests. Results The prevalence of clinically significant insomnia (ISI ≥10) was 27.1% (95% CI: 19.9%-35.8%). According to ISI classification, 58.5% of participants had no insomnia, 37.3% had subthreshold insomnia, 3.4% had moderate clinical insomnia, and 0.8% had severe insomnia. Compared to participants without insomnia, those with subthreshold insomnia had significantly longer auditory (p < 0.001) and visual RTs (p = 0.002), and higher DASS-21 scores (p < 0.001), but no significant differences in HRV indices or body composition. Correlation analysis showed that ISI scores were positively associated with auditory RT (r = 0.456, p < 0.001), visual RT (r = 0.247, p = 0.007), and DASS-21 scores (r = 0.508, p < 0.001). Conclusions Insomnia was highly prevalent among medical students and was significantly associated with poorer psychomotor performance and greater psychological distress, though not with HRV or body composition. These findings suggest that the cognitive and psychological consequences of insomnia may manifest earlier than autonomic or metabolic alterations in young adults. Early screening and targeted interventions are warranted to promote sleep health in this vulnerable population.