A Retrospective Study Suggests that Chronic Insomnia Behaves as a Neurodegenerative Disorder

Abstract

Insomnia is a prevalent sleep disorder. We examined chronic insomnia in terms of subjective and objective measures, according to self-reported duration of disorder. 443 patients were included from a sleep clinic diagnosed with chronic insomnia (ICSD3 criteria). Patients were retrospectively evaluated in terms of medical interview, sleep questionnaires, a standard polysomnography study, and subdivided in subgroups according to disorder duration. We compared patient’s results to a control group. Insomnia and control groups were significantly different in terms of TST, SE, SOL, N1 sleep, REM sleep, REM latency and number of REM episodes (p<0.05). For the group of ≤1 year of insomnia disorder all PSG parameters were statistically different from controls, except N2% and N3%, REM latency, and number of REM episodes. In the groups of 2 to 4 years, 10 to 19 years, and ≥ 20 years of insomnia we found the same differences except for REM sleep. On the contrary, in a subgroup analysis of 5 to 9 years of insomnia disorder duration, no differences to control group were found in TST, N1 or REM sleep to control group, adjusted for age. The polysomnographic sleep profile of chronic insomnia patients is different over time. It sketches an initial attempt of compensation in initial years of insomnia, which seems to disappear in long time chronic insomnia patients, as we usually see in others neurodegenerative disorders. Future studies are needed to clarify the natural history of chronic insomnia disorder and its behaviour as a neurodegenerative disorder.