Validation of insomnia questionnaires in the general population: The Nord-Trondelag Health Study (HUNT)

The primary aim was to validate questionnaire-based insomnia diagnoses from a modified Karolinska Sleep Questionnaire (KSQ) and the Insomnia Severity Index (ISI), by age category (< or >65 years), against a semi-structured face-to-face interview. Secondary aims were to split validity by diagnostic certainty of the interview and to compare prevalence estimates of questionnaire- and interview-based diagnoses. A total of 232 out of 1,200 invited (19.3%) from the fourth Nord-Trondelag Health Study (HUNT4) completed questionnaires, including the KSQ and ISI, shortly before attending a face-to-face diagnostic interview for insomnia based on the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Both a tentative (DSM-5 criteria A-E) and a definite (criteria A-H) interview diagnosis was evaluated. Cohen's kappa statistic quantified questionnaire validity. In all, 33% (95% confidence interval 27-39%) of participants had definite insomnia: 40% of women and 21% of men. The ISI (cut-off 12) and several KSQ-based diagnoses showed very good validity (kappa <= 0.74) against the tentative, versus good validity (kappa <= 0.61) against the definite interview diagnosis. Short questionnaires, requiring a daytime symptom at least three times a week, may underestimate insomnia prevalence. Validity was consistently higher for persons aged below versus above 65 years (definite insomnia: kappa <= 0.64 vs. kappa <= 0.56). Our results have implications for epidemiological population-based studies utilising insomnia questionnaires.

Automated summary

This study aimed to validate questionnaire-based insomnia diagnoses against face-to-face interviews, showing higher validity in individuals under 65 years old, and suggesting that short questionnaires may underestimate insomnia prevalence due to the requirement of daytime symptoms at least three times a week.