Sleep and Multiple Sclerosis: An Intriguing and Promising Relationship

Multiple Sclerosis (MS) is one of the most debilitating neurodegenerative disorders, with the highest incidence of onset between the second and the fourth decade of life; it affects approximately 2.4 million people worldwide [1]. Although the etiopathogenesis of the disease has not been fully elucidated, the effects of MS on the brain are known: the appearance of focal areas of demyelination and inflammation, reactive astrogliosis, and loss of neurons and oligodendrocytes [2]. The damage to the brain and spinal cord is initiated by T-cell-mediated inflammation, and demyelination and neurodegeneration are driven by several mechanisms involving the innate and adaptive immune systems [3]. The relationship between sleep and MS is suggested by the high incidence of sleep disorders in the MS patient population: more than half (4 times higher than in the normal population) have insomnia, sleep disorders, or breathing (Sleep-Disordered Breathing, SDB) and motor disorders [4]. Empirical evidence in recent years has highlighted the fact that MS is a disease with a multifactor etiology, and this understanding has led research to focus on modifiable factors that could have an impact on the risk of developing the disease, or disease progression, and on the poor quality of life of the patient. There is still no clarity as to what causes demyelination, neuronal loss, and astrogliosis. Among the various hypotheses, the crucial role of certain cytokines that contribute to the processes of neuroinflammation, immune dysregulation, and neurodegeneration, would seem to be confirmed [5]. Sleep fits into this scenario as it is closely correlated with some of the factors involved in these pathogenic processes: the relationship between sleep and the immune system is already known, and the growing evidence linking sleep disturbances to Alzheimer’s disease suggests a close relationship with neurodegenerative processes as well.