Comparison of impact of insomnia on depression and quality of life in restless legs syndrome/Willis-Ekbom disease and primary insomnia patients

Background: Although insomnia is common among people with restless legs syndrome (RLS), its impact on the daily suffering of those with RLS remains unclear. This study aimed to compare the differential impact of clinical insomnia on depression and quality of life (QoL) among people with RLS, primary insomnia, and healthy controls. Methods: A total of 148 people with RLS, 115 with primary insomnia, and 117 healthy controls were enrolled into this cross-sectional study. Participants completed sleep, depression, and QoL questionnaires. Clinical insomnia was defined as Korean version of the Insomnia Severity Index (K-ISI) ≥ 15. Correlation coefficients between sleep measures and both depression and QoL were calculated. Multivariate regression was used to identify the clinical factors that were most closely associated with depression and QoL among people with RLS and primary insomnia. Results: Participants with RLS had insomnia and sleep quality at intermediate levels between the healthy controls and primary insomnia subjects, but those with clinical insomnia had equivalent depression and QoL scores regardless of RLS diagnosis. Insomnia severity correlated with depression and QoL in RLS and primary insomnia. Multivariate regression, however, revealed that RLS severity was the most overall predictive factor for depression and QoL among those with RLS. Insomnia severity was the strongest predictor in primary insomnia. Conclusion: Insomnia was more closely associated with depression and QoL among people with primary insomnia than those with RLS, but clinical insomnia may have a significant impact in RLS as well. Future RLS studies should account for sleep quality in addition to RLS symptom severity when investigating mood and QoL.