Sleep apnoea and sleep disruption in multiple sclerosis: Rates, mechanisms and consequences

Prevalence rates, mechanisms and consequences of sleep disorders in people with MS are unclear. Accordingly, in Study 1, I investigated rates of sleep disorders and poor sleep quality in a consecutively recruited cohort (n=111) of people with mild to moderately-severe MS. I used a comprehensive sleep assessment battery that included a home-based sleep study, validated sleep questionnaires and actigraphy. >50% had a sleep disorder (sleep apnoea 31%, insomnia 29% and restless legs syndrome 25%). 66% reported poor sleep. Poor sleep and insomnia were significant predictors of fatigue and depression. Actigraphy showed prolonged periods lying down. Increased time spent lying over a 24-hour period was associated with poorer subjective sleep quality. Common sleep apnoea screening questionnaires had similar performance characteristics to those reported in non-MS populations. In Study 2, the Study 1 cohort was reassessed six months after a home-based step-training exercise intervention. The intervention group (n=53) was encouraged to perform 2h training per/week, while controls (n=58) continued usual physical activity. Step-training exercise did not change perceived or objective sleep quality or sleep apnoea. However, the odds of having excessive daytime sleepiness at reassessment were lower in the intervention group. Changes in sleep quality correlated with changes in fatigue, depression and sleepiness. While there was individual variability in certain sleep parameters, on average, sleep parameters were stable at 6-month follow-up. In Study 3, I investigated mechanisms of sleep apnoea in MS. The reflex responses to brief pulses of negative pharyngeal pressure of the largest upper-airway dilator muscle, genioglossus, were compared in people with sleep apnoea with versus without MS (n=11/10). There was no systematic difference in reflex responses between groups. However, ~30% of the MS group had an absent or abnormal response which was not seen in the controls. The two MS participants without a reflex response had multiple brainstem demyelinating lesions with an extensive lesion affecting the hypoglossal nucleus bilaterally. In summary, these findings highlight the major impact that sleep disorders and sleep disruption have on important comorbidities in people with MS and provide novel insight into a potential unique cause of sleep apnoea in certain people with MS