Medical interns and health challenges: insights into physical inactivity, sleep disruption, and body metrics

Becoming a medical intern (MI) represents a major transition in medical education. During this period, trainees are exposed to demanding clinical environments that challenge endurance, adaptability, and self-care. Irregular schedules, sleep deprivation, and reduced opportunities for physical activity (PA) frequently accompany this phase and may lead to measurable changes in anthropometric and body composition (BC) parameters. This study aimed to evaluate one-year changes in BC, PA, and sleep quality (SQ) among MIs and to explore their interrelationship.

A longitudinal observational study was conducted in 170 MIs (18-25 years) at a Mexican public university hospital, assessed at baseline and after 12 months. Anthropometric and BC parameters were obtained using multifrequency bioimpedance analysis (InBody 270S). PA was assessed with the Global Physical Activity Questionnaire (GPAQ), and SQ with the Pittsburgh Sleep Quality Index (PSQI). Group comparisons were performed using parametric or non-parametric tests as appropriate, with effect sizes reported as Cohen's d and Cramér's V. Statistical significance was set at p < 0.05.

Participants had a mean age of 22.9 ± 0.87 years; 62.0% were female. Body mass index (BMI) increased from 25.47 ± 5.06 to 26.22 ± 5.31 kg/m² over the follow-up period. Total body water (TBW), protein mass (PM), and mineral mass (MM) showed relative reductions, while body fat mass (BFM) increased, and skeletal muscle mass (SMM) remained largely stable. The proportion of MIs classified in the low PA category decreased, whereas those engaging in high PA increased. Overall SQ deteriorated, with fewer participants reporting good SQ and a higher proportion classified as poor SQ. Males demonstrated greater increases in BFM, whereas females exhibited relatively more favorable SQ profiles. No significant association was observed between PA level and PSQI-defined SQ.

Despite modest improvements in PA patterns, MIs experienced worsening SQ and unfavorable shifts in BC during the internship year. These findings underscore the vulnerability of medical interns to lifestyle-related health changes and highlight the need for institutional wellness strategies focused on sleep hygiene, balanced nutrition, and sustained opportunities for PA.