The Reliability of a New Sleep Screening Questionnaire for Large Population-Based Studies: The Third Nord-Trøndelag Health Study

The aim of the present study was to evaluate the reliability of a new sleep questionnaire (sHUNT-Q) used in the Nord Trøndelag Health Study 3 (HUNT 3) performed between 2006 and 2008. Six of nine items were modified from a Norwegian version of the Karolinska Sleep questionnaire (KSQ). Overall, 50,839 (54%) out of 94,194 invited participated in HUNT 3. In a randomly selected group of participants, 297 (53%) out of 563 invited persons attended an interview by neurologists. The reliability of the sleep related questions was evaluated with Cohen ́s kappa by blindly comparing the answers in the questionnaire with those from the semi-structured interview. Summary measure scores were calculated by summing the responses of the six modified KSQ questions, the three insomnia-related questions, and the two questions related to respiratory disturbance during sleep. Agreement was calculated for dichotomized sum-score indexes based on 75% and 50% percentile cut-offs. Kappa values for the individual questions ranged from 0.35 to 0.52 in 3 x 3 tables while kappa for summary indexes in 2x2 tables ranged from 0.47 to 0.62. The best agreement between the interview and the questionnaire was found for respiratory disturbance defined as a summary measure score 50 percentile (kappa value 0.62, 95% CI 0.51-0.74). Reliability did not depend on the time between the HUNT questionnaire and the interview. The KSQ-based summary measure scores from the new sHUNT-Q sleep screening questionnaire may become a useful tool in epidemiological studies for identifying individuals with a persistent sleep disturbance.