La somnolence diurne excessive et les hypersomnies centrales primaires : données épidémiologiques

Excessive daytime sleepiness is a symptom with a high prevalence in the general population. The huge variability in the prevalence of excessive daytime sleepiness is partly due to different and inadequate methodologies. In adults, chronic and moderate daytime sleepiness is observed in 15 to 20% of the subjects, and severe sleepiness in 6 to 11%. The prevalence may vary according to numerous factors. Age is one of these factors; daytime sleepiness is more frequent in adolescents and older subjects. Several factors and pathological conditions are independently and significantly linked to excessive daytime sleepiness. Among sleep disorders, snoring, obstructive sleep apnea syndrome, central hypersomnias, delayed sleep phase and chronic sleep debt are found significantly associated with excessive daytime sleepiness. Moreover, other diseases such as psychiatric illness and especially depression, obesity or excessive weight, and diabetes are significantly related to daytime sleepiness. In old subjects, a very significant relationship is found between excessive daytime sleepiness and cognitive decline or dementia, and with cardiovascular disease and mortality. Excessive daytime sleepiness is very often multi factorial. It is very important to recognize and treat daytime sleepiness to prevent its deleterious consequences. Among central primary hypersomnias, the prevalence of narcolepsy with cataplexy falls between 34 and 50 per 100,000 people. The incidence is not well known, one study finding the incidence to be 0,74 per 100,000 person-year. The origin of the loss of orexine neurons is not known but the onset of the disease is likely linked to environmental exposures and auto-immune process, in genetically susceptible individuals. The study of familial forms of the disease led to the conclusion that between 11 and 21% of narcoleptic probands had at least one family member with narcolepsy. Nothing is known about the prevalence of idiopathic hypersomnia, which is even rarer than narcolepsy.