Validity, reliability, and responsiveness of the work productivity and activity impairment in patients with insomnia disorder

Abstract Objectives This study aimed to evaluate the validity, reliability, and responsiveness of the work productivity and activity impairment (WPAI) in patients with insomnia disorder. Methods A total of 1075 patients with insomnia disorder were recruited. Convergent validity was assessed by correlations between the WPAI outcomes (absenteeism, presenteeism, overall work productivity loss, and activity impairment) and Insomnia Severity Index (ISI), Patient Health Questionnaire‐9 (PHQ‐9), Generalized Anxiety Disorder‐7 (GAD‐7), and quality‐adjusted life years (QALYs). Known‐group validity was tested by comparing the WPAI outcomes between groups with differing symptom severity. Responsiveness was evaluated by comparing WPAI score changes between responders and nonresponders based on the minimum clinically important difference of ISI. Test–retest reliability was calculated using intraclass correlation coefficient (ICC) in clinically stable patients over 3 months. Results All WPAI domains were significantly correlated with ISI, PHQ‐9, GAD‐7, and QALYs scores ( r = 0.20–0.46, all p < 0.001). Patients with greater symptom severity had significantly higher WPAI scores (all p < 0.001). Clinical responders showed statistically greater decreases in presenteeism, overall work productivity loss, and activity impairment (all p < 0.001). WPAI represented moderate stability (ICC = 0.56–0.69) over 3 months except for absenteeism (ICC = 0.41). Conclusions The WPAI is a valuable instrument for assessing work productivity and activity impairment in patients with insomnia disorder.