Prevalence of ‘poor sleep’ among patients with multiple sclerosis: An independent predictor of mental and physical status

Abstract

Background

Patients with multiple sclerosis (MS) report sleep disturbances more frequently than the general population. Besides specific sleep disturbances, many other conditions could impair nocturnal rest in this population. In addition, information regarding the role of disrupted sleep on quality of life (QoL) in MS patients is lacking. This study was performed to bridge this gap.

Methods

A total of 120 patients with MS were enrolled into the study. Demographic, socioeconomic and clinical characteristics (clinical course and duration of MS, EDSS score, therapeutic information, presence of pain, presence of sexual and/or bladder dysfunction, localization of demyelinating plaques, and presence of anxiety and depression) were collected. The Pittsburgh Sleep Quality Index (PSQI), the Charlson Comorbidity Index (CCI) and the Italian version of the 36-item Short Form (SF-36) were used to assess quality of sleep, comorbidity and QoL, respectively.

Results

Nearly half (47.5%) of MS patients were classified as “poor sleepers,” having significantly higher EDSS (3.1 ± 1.4 vs. 2.3 ± 1.4, p = 0.009) and CCI scores (0.19 ± 0.4 vs. 0.03 ± 0.2, p = 0.009) than “good sleepers.” In addition, pain due to MS was more common among “poor sleepers” (33.3% vs. 17.7%, p = 0.05). Scores for each domain of the SF-36, and the mental component summary (MCS) and physical component summary (PCS) scores were significantly lower in poor sleepers than in good sleepers (p < 0.001 for each score). Of the different variables associated with MCS, the only independent predictors of mental status were: presence of sexual and/or bladder dysfunction and global PSQI score. The independent predictors for physical status (PCS) were age, EDSS score and global PSQI score.

Conclusions

Poor sleep is common in patients with MS, representing an independent predictor of QoL. Patients with MS who are poor sleepers should receive immediate assessment and treatment, bearing in mind that, in addition to specific sleep disturbances, other clinical conditions (both related and unrelated to MS) can disrupt nocturnal sleep.

Introduction

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system with onset generally between the ages of 20 and 50 years. Patients with MS report sleep disturbances more frequently than the general population, and may be affected by the entire spectrum of sleep disorders (i.e., insomnia, excessive daytime sleepiness, periodic leg movements, restless legs syndrome, abnormal sleep–wake regulation, sleep-disordered breathing, narcolepsy and rapid eye movement sleep behaviour disorder, etc.) [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12]. Two polysomnographic studies performed on patients with MS showed that sleep macro- and microstructure were markedly altered in this patient group, with a higher number of nocturnal awakenings, a higher level of wake time after sleep onset and a higher total arousal index, and a lower sleep efficiency index compared with controls [7], [8]. Even though disrupted nocturnal rest might be directly related to specific sleep disturbances, many other demographic and clinical conditions (e.g. presence of comorbidities, MS duration and progression, medication effects, experience of pain and sexual and/or bladder dysfunction, anxiety and depression) should be considered as possible causes of sleep disorders in patients with MS. To our knowledge, the role of demographic, socioeconomic and clinical variables on sleep quality in patients with MS has never been carefully evaluated.

Several studies, performed in Italian patients affected by MS, have shown that this neurological disease has a highly negative impact on quality of life (QoL) [13], [14]. Many factors seem to be implicated in the impairment of QoL in patients with MS: a progressive disease course [13], [15], [16], [17], extended disease duration [18], physical disabilities [16], [19], [20], emotional and cognitive impairment [13], [17], [20], sexual and/or bladder dysfunction [21] and interferon (IFN) beta treatment [22] represent the main predictors of poor QoL in this population. Unfortunately, only one of the studies conducted to date has included sleep quality among the variables potentially related to QoL [23], but in this study the only independent predictors of the global quality of life index score were found to be depressive mood and physical disability; quality of sleep was an independent predictor only of physical well-being.

The aims of our study were: (i) to examine the prevalence of “poor sleepers” and (ii) to evaluate the role of demographic, socioeconomic and clinical variables on sleep quality among patients affected by MS, and (iii) to analyse the association between quality of sleep and QoL while controlling for known and unknown possible predictors of QoL in patients with MS.