The association of comorbidities with sleep quality among Australians with multiple sclerosis: Insights from the Australian Multiple Sclerosis Longitudinal Study

BACKGROUND: Comorbidities and poor sleep quality are prevalent among individuals with multiple sclerosis (MS). Our understanding of the effects of comorbidities on sleep quality in MS remains limited. OBJECTIVES: The objectives were to investigate whether the number and presence of specific comorbidities have associations with sleep quality and to assess the relative contribution of comorbidity groups to sleep quality. METHODS: We collected data on sleep quality (using Pittsburgh Sleep Quality Index (PSQI)) and presence of comorbidities in people with MS (n = 1597). Associations between comorbidities and sleep quality were examined using linear regression and dominance analysis. RESULTS: Having more comorbidities was associated with poorer sleep quality (p for trend < 0.001). All 13 groups of comorbidities explained 12.9% of the variance in PSQI from which half of the variance was contributed by mental health disorders. In total, 16 of the 28 comorbidities were associated with significantly worse sleep quality, with the strongest associations seen for 'other autoimmune diseases' (β = 1.98), depression (β = 1.76), anxiety (β = 1.72) and rheumatoid arthritis (β = 1.62). CONCLUSIONS: Many individual comorbidities are associated with poorer sleep quality, with mental health disorders making the largest relative contribution. Optimal management of comorbidities that make the greatest contributions could have the largest benefit for improving sleep in MS.