<![CDATA[Background. Medical training imposes schedules that structurally conflict with biological timing. Literature on sleep in medical students has grown rapidly, yet how much of it measures a circadian dimension remains unclear. Objective. To map the distribution, design and quality of evidence on circadian disruption and sleep in medical students, and to distinguish objective circadian assessment from indirect measures. Methods. A structured PubMed search was run to 23 September 2026. All records were screened using mutually exclusive exclusion categories, with a documented reason for each record. Data were extracted using a 23-variable matrix. Risk of bias was appraised with design-appropriate instruments and reported in each instrument's native output, without composite scores. Circadian assessment was classified as A, A−, B+, B−, B or C. Synthesis was narrative, presented as an evidence map; no meta-analysis was performed. Results. Of 710 records, 626 were excluded at screening and 84 assessed for eligibility; 8 were excluded and 3 reassigned to context, leaving 73 studies plus 2 from other sources, giving 75 studies in the evidence map. Full text was verified for 49 studies; 26 were abstract-only, 4 flagged as having limited information. Designs were predominantly cross-sectional (47 studies). Objective, direct circadian assessment was found in only 3 studies, with a further 3 using partial objective indicators. Risk of bias could be appraised in 55 studies but not in 20. Conclusion. The evidence base rests almost entirely on cross-sectional designs using indirect circadian measures, so mechanistic circadian claims are not yet supported by direct evidence]]>
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