Assessing the reliability and validity of sleep assessments in patients seeking metabolic and bariatric surgery

Background: More than 80% of patients seeking metabolic and bariatric surgery (MBS) report disturbance in sleep function. No studies have assessed the psychometric properties of sleep measures in MBS samples. Objectives: This study assessed the reliability and validity of the Pittsburgh Sleep Quality Index (PSQI) and the Insomnia Severity Index (ISI) in a large sample of patients seeking MBS. Setting: Two academic medical centers. Methods: Measures of sleep (PSQI and ISI) and psychological functioning, including the Quick Inventory of Depressive Symptomatology (QIDS), were administered presurgically. Internal consistency was assessed with mean inter-item correlations and item-total correlations. Construct validity was assessed using confirmatory factor analyses (CFAs) based on models identified in the literature and by measuring convergent and discriminant validity. Results: Participants (N = 939) were primarily female (83.4%) with a mean age of 41.7 (SD = 11.5) years and mean body mass index (BMI) of 47.5 kg/m² (SD = 8.5). CFAs indicated excellent fit for 2-factor solutions for the PSQI and ISI. Internal consistency for the PSQI and ISI were acceptable. Convergent validity was demonstrated by large correlations between the PSQI and ISI (r = .80, p < .001), and moderate correlation between the PSQI, ISI, and QIDS (rs > .50, ps < .001). The PSQI and ISI were moderately correlated with QIDS items assessing sleep function (P < .001), but correlations with items assessing appetite change were small (r < .10), demonstrating good discriminant validity. Conclusions: Results support the reliability and validity of the PSQI and ISI for patients undergoing MBS.