Insomnia in medical students during an examination period: associations with depression, dysfunctional sleep beliefs, and academic performance.

Nearly half of medical students screened positive for clinically relevant insomnia symptoms during an examination period.

• 46.0% (57/124) of students scored above the ISI threshold (ISI > 10), indicating clinically relevant insomnia symptoms.
• The survey was conducted at a German medical school during a fourth-year exam period.
• Total sample size was 124 students.
• The Insomnia Severity Index (ISI) was used as the primary outcome measure.

Students with clinically relevant insomnia symptoms had significantly worse objective sleep parameters compared to those without.

• Shorter total sleep time: 391.0 ± 76.5 vs. 438.2 ± 58.3 minutes (P < 0.001).
• Longer sleep onset latency: 51.1 ± 37.1 vs. 21.6 ± 18.0 minutes (P < 0.001).
• Lower sleep efficiency: 82.2% ± 12.2% vs. 90.1% ± 7.2% (P < 0.001).
• Sleep parameters were assessed using selected items from the Pittsburgh Sleep Quality Index (PSQI).

Higher depressive symptoms were independently associated with greater insomnia severity in adjusted analyses.

• PHQ-9 score was a significant independent predictor of ISI (β = 0.30; P = 0.01).
• This association remained significant after adjusting for other state and trait variables.
• The multivariable model explained 57.2% of variance in ISI (R² = 0.572; adjusted R² = 0.523).
• Depression was measured using the Patient Health Questionnaire-9 (PHQ-9).

Dysfunctional sleep beliefs were independently associated with greater insomnia severity in adjusted analyses.

• DBAS-16 total score was a significant independent predictor of ISI (β = 0.28; P < 0.001).
• Dysfunctional sleep beliefs were measured using the Dysfunctional Beliefs and Attitudes about Sleep Scale-16 (DBAS-16).
• The association remained significant after controlling for state variables including stress, anxiety, and chronotype.
• The authors note that dysfunctional sleep beliefs are 'relatively stable cognitive traits' that 'remain amenable to targeted interventions.'

Higher sleep efficiency and better academic performance were each inversely associated with insomnia severity.

• Higher sleep efficiency was inversely associated with ISI (β = -0.30; P < 0.001).
• Better academic performance was inversely associated with ISI (β = -0.15; P = 0.037).
• Both associations were independent in the adjusted multivariable model.
• Academic performance data were recorded as part of the study protocol.

Perceived stress, anxiety, and chronotype were not independent correlates of insomnia severity in adjusted analyses.

• Stress was measured using a visual analogue scale (VAS).
• Anxiety was measured using the Generalized Anxiety Disorder-2 (GAD-2).
• Chronotype was assessed using the reduced Morningness-Eveningness Questionnaire (rMEQ).
• Despite being state-level factors expected to relate to insomnia, none reached independent significance in the multivariable model.

Among DBAS-16 subscales, Worry/Helplessness and Perceived Consequences were significantly associated with higher insomnia severity.

• A secondary regression model examined DBAS-16 subscales as predictors of ISI.
• The subscale model explained 33.2% of variance in ISI (R² = 0.332; adjusted R² = 0.307).
• The Worry/Helplessness and Perceived Consequences subscales were both significantly associated with higher ISI scores.
• This model had lower explanatory power than the full multivariable model (adjusted R² = 0.307 vs. 0.523).