Elsevier

Sleep Medicine

Volume 16, Issue 11, November 2015, Pages 1403-1408
Sleep Medicine

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

https://doi.org/10.1016/j.sleep.2015.06.019Get rights and content

Highlights

  • Participants with restless legs syndrome (RLS) had better sleep quality than those with primary insomnia.

  • Insomnia severity correlated with depression and quality of life (QoL) in RLS and primary insomnia.

  • Participants with clinical insomnia had equivalent depression and QoL, regardless of RLS diagnosis.

  • RLS severity was the most predictive factor for depression and QoL in RLS.

  • Insomnia severity was the strongest depression and QoL predictor in primary insomnia.

Abstract

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.

Introduction

Restless legs syndrome/Willis–Ekbom disease (RLS/WED) is a common, sensorimotor, neurological disorder with significant impact on sleep and quality of life (QoL). Sleep disturbance is common in RLS, and both insomnia and RLS symptoms are independently associated with depression [1], [2], which further contributes to impaired QoL [3]. An estimated 50–85% of people with RLS suffer from initial or sleep-maintenance insomnia [4], [5], [6], [7], [8], [9], [10], [11], and insomnia is more common among those with greater symptom severity [11], [12]. In particular, depression is common in RLS, with a prevalence ranging from 10 to 50% [13], [14], [15], and the presence of RLS has been associated with a higher risk of clinical depression, greater severity of depression scores, and lower internal locus of control [13], [16], [17], [18], [19], [20].

In the general population, insomnia is closely associated with depression [21], [22] and impaired QoL [23], [24], [25], but effective insomnia treatment may improve these outcomes [26], [27], [28]. Depression is also closely associated with impaired QoL in several medical conditions [29], [30], [31], [32], [33]. In RLS studies in particular, both insomnia and depression have been associated with fatigue, poor social functioning, and poor QoL [10], [12], [34], [35], and electroencephalographic evidence of sleep fragmentation in RLS predicts poor psychological function at follow-up nearly three years later [36].

The impact of insomnia on depression and QoL in people with RLS, however, remains unclear. Previous findings have been inconsistent. For instance, one longitudinal study of people with RLS was unable to find an association between depression and sleep disturbance [37], whereas in a cohort of patients with chronic kidney disease, insomnia mediated a portion of the association between RLS and depression [38]. Further, using structural equation modeling, sleep disturbances were shown to mediate a significant component of emotional distress among subjects with RLS [39]. It is believed that, to date, no previous study has compared the impact of insomnia symptoms on depression and QoL among people with RLS and primary insomnia.

Following the previous work by Brand et al. [36], it was hypothesized that there is an association between insomnia and both depression and QoL among people with RLS and primary insomnia, and that this association is stronger among subjects with primary insomnia than those with RLS. To test this hypothesis, the impact of insomnia on depression and QoL was compared among people with RLS, primary insomnia, and healthy controls.

Section snippets

Participants

The institutional ethics committee of the regional hospital approved this study. The target population included 263 drug-naïve people – 148 with primary RLS and 115 with primary insomnia – who were evaluated at a tertiary-care sleep center between August 2010 and November 2013. A certified Korean neurologist, who was an expert in sleep medicine (YWC), evaluated each person with RLS or primary insomnia. Each person with RLS met the 2014 Revised International Restless Legs Syndrome Study Group

Comparison of general characteristics and the features of restless legs syndrome

A total of 148 people with RLS, 115 with primary insomnia, and 117 healthy controls were enrolled. There were no significant differences in age, gender, or body-mass index (BMI) among the groups. In the RLS group, 38 (25.7%) participants had a family history of RLS. The RLS group had a mean age of RLS onset of 42.45 years (±12.79), symptom duration of 8.09 years (±8.58), mean ferritin level of 67.22 ng/mL (±65.45), mean K-IRLS of 27.69 (±6.41), and mean K-RLSQol of 59.54 (±22.57) (data not

Discussion

Insomnia is a common comorbidity in people with RLS [7], [9], [12], [20], and depressed mood commonly occurs in people with both RLS and primary insomnia [50]. Insomnia prevalence among the participants with RLS in the present study was 62.2%, which is toward the higher end of the range of previous reports [4], [5], [6], [7], [8], [9], [10], [11]. Also in this study, depression of at least moderate severity (BDI score of ≥20) occurred in 37.8% of participants with RLS, which was higher than the

Conflict of interest

All authors have no conflicts of interest.

The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2015.06.019.

. ICMJE Form for Disclosure of Potential Conflicts of Interest form.

Acknowledgements

This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea Government (MSIP) (No. 2014R1A5A2010008).

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