Importance of sleep in the quality of life of multiple sclerosis patients: A long under-recognized issue

In our concentrated attempts to find treatments and cures for disease we often ignore the most important aspect of a life lived with chronic illnesses, namely its quality. There are only a handful of studies specifically addressing this issue in patients with multiple sclerosis (MS) and until now none having looked specifically at sleep as a determinant of quality of life.

It is intuitive that chronic and persistent poor sleep leads to poor quality of life. There are a number of studies that validate this relationship in patients with sleep disorders and a few that have looked at sleep and quality of life in other chronic illnesses. The study of both normal and abnormal sleep in neurological illnesses is only recently gaining momentum, especially in degenerative disorders and epilepsies. The impact of sleep disturbances in MS has so far received little attention in research. Literature on this subject falls roughly into two categories: prevalence of sleep disorders in MS and the relationship of sleep disturbances and fatigue.

Since the 1960s there have been sporadic reports of different sleep disorders in MS, including narcolepsy [1], [2], hypersomnia with low CSF hypocretin levels [3], periodic limb movement disorder, habitual snoring, nocturia [4] and conflicting papers on the prevalence of restless legs syndrome and REM Behavior disorder [5], [6]. Studies exploring the relationship of fatigue (the most disabling symptoms of MS) and sleep disturbances unanimously show a definite relationship between the two [7], [8], [9]. Of note, sleep disturbances are a major but not exclusive factor contributing to fatigue since it is clearly recognized that fatigue in MS is multifactorial [10].

In 2004 Lobentanz et al. looked at different factors impacting quality of life in a group of MS patients. Depression was found to be the main determinant of poor quality of life followed by fatigue and sleep disturbances [11]. The quality of life questionnaire used, however, was the Quality of Life Index (QLI) which does not have items directly related to fatigue or sleep. A more recent study by Spain et al. published earlier this year demonstrated that illness perception itself is an independent determinant of quality of life in patients with MS [12]. Until now, there have been no studies isolating sleep issues from fatigue and depression and observing sleep disturbances as an independent variable in quality of life in MS.

The current issue of this journal contains an interesting paper by Merlino et al. entitled “Prevalence of ‘poor sleep’ among patients with multiple sclerosis: an independent predictor of mental and physical status,” demonstrating that poor sleep is an independent predictor of poor quality of life. In this elegantly designed study the investigators used the Pittsburgh Sleep Quality Index (PSQI) to assess sleep quality, the Charlston Comorbidity index to isolate comorbidities that can have an impact on quality of life and the well validated SF-36 for quality of life. The SF-36, as opposed to the QLI used in the older study, includes sleep and fatigue related items and it is validated. Sleep disturbances impact the overall physical and mental well being of patients with MS, contributing to previously recognized predictors of poor quality of life including depression, fatigue and pain. This is also very well illustrated in the Merlino et al. study. As a side note, since there are different scales for quality of life being used in different studies maybe it is time to create a well validated MS-specific quality of life questionnaire.

It is important to recognize the role of sleep disturbances in the quality of life of people with MS to provoke further discussion about these disturbances and their causes. This may potentially lead to a more timely diagnosis and treatment, which would not only improve the MS patient’s quality of life, but could also prevent serious health consequences. In addition, improving sleep will improve depression, perception of pain, and may even have an impact on one’s fatigue, thereby positively impacting quality of life. Strober and Arnett in 2005 proposed a nicely illustrated model of the relationship among depression, fatigue, sleep disturbances and overall disease severity [13]. Sleep disturbances, unlike depression and fatigue, can be easily quantified by tools such as actigraphy and polysomnography. This becomes useful in trying to improve quality of life in patients where self assessment is difficult and proxy assessments are inaccurate [14].

At the Vermont Regional Sleep Center we are in the process of studying the impact of eliminating sleep disturbances on the severity and presence of fatigue and cognitive function.

Getting a good night’s sleep may not cure or even improve the neurological damage of MS, but it would certainly help people face it with a better outlook and give them a better chance at a fuller life. The similarities between the MS sleep disturbances and those in rheumatoid arthritis and end stage renal disease were demonstrated in a 1993 study [15]. But there needs to be more research devoted to the relationship of sleep and quality of life in other chronic conditions similar to the paper discussed above.

We are far from finding cures for all chronic illnesses, so meanwhile it is important that we try to address the quality of life for those living with disease and disability.