Sleep seasonality in alpha-synucleinopathies: A comparative study with non-neurological sleep disorder patients

Introduction: It is unknown if seasonal variation in daylight affects sleep in patients with alpha-synucleinopathies. Our objectives were to assess month of the year related changes in polysomnography (PSG) data in patients with Parkinson 's disease (PD), Lewy Body Dementia (LBD) and isolated REM sleep behavior disorder (iRBD). Methods: We collected PSG data from 64 PD, 30 LBD and 24 iRBD patients attending a sleep laboratory in Lisbon, Portugal, during 10 years. Each was classified according to the month of the year PSG was performed and compared with a control patient with sleep disorder, but no evidence of other neurological disorder, matched for sex, age group and PSG month. The influence of month in PSG data was assessed with mixed linear regression analysis.Results: In alpha-synucleinopathies, month showed significant interaction with N2 stage time and percentage (increase from December to April) and N3 time (peak in May). REM sleep percentage increased significantly from Spring to middle Summer. In the control group, there were significant interactions regarding Total Sleep Time and Sleep Efficiency (drop during wintertime), N2 time and REM % (increase in April and May) and ApneaHypopnea Index (AHI) (peak in June). There were significant associations between the term group*month and sleep efficiency and AHI, with larger monthly variation in the control group.Conclusion: Seasonality had a larger impact in stage architecture in alpha-synucleinopathies, and in total sleep time, sleep efficiency and the severity of OSA in the control group. Different sleep dysfunction mechanisms could explain differences in seasonal variation.