Psychometric evaluation of the Nocturia Sleep Quality Scale based on data from a prospective observational study

The Nocturia Sleep Quality Scale (NSQS), a novel patient-reported outcomes measure, was developed to assess the impact of sleep disturbance from nocturia. The objective of this study was to assess the psychometric properties of the NSQS, including its structure, reliability, and validity.

Data were collected in the context of a web-based, prospective, longitudinal, observational study. Participants with nocturia were randomized 1:1 to either a group that received sleep hygiene instructions, including instructions to limit liquids at nighttime and empty bladder prior to bedtime, or one that did not receive sleep instructions. All participants were asked to provide responses to the web-based questionnaires from day 1 to day 10. Psychometric analyses, aligned with current regulatory guidance, were conducted to evaluate the daily scores and 3-day average scores of NSQS items and potential composites. Item-level analyses were conducted first, followed by composite-level analyses.

The NSQS items and supporting measures demonstrated very slight improvement in patient-perceived sleep disturbance from nocturia over the course of the study. NSQS test-retest reliabilities were generally satisfactory. Correlations between NSQS items and related patient-reported measures tended to support the construct validity of the NSQS, and the known-groups analyses supplied evidence of its discriminating ability. NSQS responsiveness statistics were small.

The NSQS is a reliable and valid measure of the impact of nocturia on patients' sleep. The present analyses lay the psychometric groundwork for the use of the NSQS in future clinical trials to support product approval and labeling claims.