Prevalence of Possible Rem Sleep without Atonia in the General Population: Insights from the São Paulo Epidemiologic Sleep Study (EPISONO).

Introduction: The aim of this study was to estimate the prevalence of possible rapid eye movement (REM) sleep without atonia (RWA) in the general population.

Methods: The study was based on data from the São Paulo Epidemiologic Sleep Study (EPISONO) 4th edition, a non-clinical population-based sleep study performed in the city of São Paulo, Brazil, between 2018 and 2019. All individuals underwent type-I polysomnography with the addition of bilateral electromyography of the flexor digitorum superficialis (FDS) muscles. The FDS activity index was calculated as the percentage of 30-s REM sleep epochs containing at least five 3-s mini-epochs with phasic muscle activity, with a threshold of 7.7% being applied to identify possible RWA cases. The adjusted prevalence of possible RWA was calculated as the proportion of cases above the diagnostic threshold, corrected by the estimated specificity values according to the REM-specific apnea-hypopnea index (AHI; 85% for REM AHI <15 and 60% for REM AHI ≥15).

Results: The final sample comprised 632 participants (376 females, 59.49%), and 68 possible RWA cases were identified. The adjusted prevalence of RWA in the whole sample was 8.24% (95% CI: 6.09%-10.38%). The adjusted prevalence stratified by sex was 10.63% among men (95% CI: 6.85%-14.40%) and 6.61% among women (95% CI: 4.10%-9.12%) (p = 0.013), resulting in a male/female prevalence ratio of 1.61. Possible RWA prevalence was similar between men and women in the 20-39 and 40-59 age ranges, but significantly higher among men aged 60-80 (16.57%, 95% CI: 6.66%-26.49%) than women in the same age range (7.35%, 95% CI: 2.62%-12.81%) (p = 0.022).

Conclusions: The prevalence of possible RWA in the sample was 8.24% and was similar between the sexes in most age ranges but became more frequent among men from the age of 60 years old.