Prevalence and predictors of REM sleep without atonia in a sleep clinic population

The burden of rapid eye movement (REM) sleep behaviour disorder is well documented, however the significance of isolated REM sleep without atonia is unclear. We evaluated the prevalence and predictors of RSWA in a sleep clinic population. We analysed data in three groups—patients meeting American Academy of Sleep Medicine (AASM) criteria for loss of REM atonia (RSWA), elevated REM EMG activity which did not meet AASM criteria (Elevated REM EMG) and those with no elevated REM EMG activity (normal). Analysis included 511 diagnostic sleep studies over 6 months. RSWA was identified in 36 (5.8%) and elevated REM EMG activity in 44 (8.6%) patients. The RSWA group, compared with the normal group, had a higher use of medications (anti-depressants, beta blockers and anti-cholinesterase inhibitor) OR 2.05 (95% CI 1.0–4.1), p = 0.04. Periodic limb movement indices in REM were different between groups: RSWA mean (95% CI) = 22.5/h, (11.0–33.9), elevated REM EMG = 8.6/h, (5.1–12.2), normal mean = 0.9/h (0.6–1.3), p < 0.0001. On multivariable analysis, male gender was also associated with RSWA OR 4.1 (95% CI 11.4–13). Body mass index (BMI) and apnoea–hypopnea index (AHI) were higher in the normal group. There were no between-group differences in age, Epworth Sleepiness Scale, Hospital Anxiety/Depression Scale scores. At our institution, there is a relatively high prevalence of RSWA and predictors include medication use, elevated REM PLMi and male gender. There is also a group of patients with elevated REM EMG activity who demonstrate similar characteristics to those meeting AASM criteria, who warrant further characterisation.