Westerland, Sarah M.

ABSTRACTBackgroundRapid eye movement (REM) sleep behavior disorder (RBD) occurs occasionally in essential tremor (ET), but polysomnographic REM sleep without atonia (RSWA) analyses have been sparse.ObjectiveTo characterize the amount and distribution of polysomnographic RSWA, the electrophysiologic substrate of RBD, in patients with Parkinson's disease (PD) and ET.MethodsWe analyzed quantitative RSWA in 73 patients: PD (23), ET (23), and age‐sex‐matched controls (27). None had dream‐enactment behavior history or received antidepressants. Phasic, tonic, “any,” and phasic‐burst duration RSWA measures were calculated in the submentalis (SM) and anterior tibialis (AT) muscles. The automated REM atonia index (RAI) was also determined. Statistical analysis was performed by Kruskal‐Wallis rank‐sum and Mann‐Whitney tests.ResultsSM phasic RSWA was significantly greater for PD than ET patients and controls (12.5% ± 12.8% vs. 4.9% ± 6.7%, 3.9% ± 2.6%), as was SM “any” (13.54% ± 14.30% vs. 5.2% ± 7.6%, 4.2% ± 2.6%). RAI was significantly lower in PD than in ET and controls (0.78 ± 0.23 vs. 0.92 ± 0.09 vs. 0.90 ± 0.17, P ≤ 0.005), but no different between ET and controls. AT phasic and “any” RSWA was similar between the 3 groups. ET and control RSWA was similar in all measures. Two ET patients (8.7%) had SM RSWA similar to PD patients.ConclusionsElevated SM RSWA distinguished PD from ET in patients without dream‐enactment symptoms and occurs frequently in PD patients, and in isolated tremor suggests underlying synucleinopathy. Prospective studies will further validate these findings.

Abstract Study Objectives Values for normative REM sleep without atonia (RSWA) remain unclear. Older age and male sex are associated with greater RSWA, and isolated elevated RSWA has been reported. We aimed to describe normative RSWA and characterize isolated RSWA frequency in adults without REM sleep behavior disorder (RBD). Methods We visually quantified phasic, “any,” and tonic RSWA in the submentalis (SM) and anterior tibialis (AT) muscles, and the automated Ferri REM Atonia Index during polysomnography in adults without RBD aged 21–88. We calculated RSWA percentiles across age and sex deciles and compared RSWA in older (≥ 65) versus younger (<65) men and women. Isolated RSWA (exceeding diagnostic RBD cutoffs, or >95th percentile) frequency was also determined. Results Overall, 95th percentile RSWA percentages were SM phasic, any, tonic = 8.6%, 9.1%, 0.99%; AT phasic and “any” = 17.0%; combined SM/AT phasic, “any” = 22.3%, 25.5%; and RAI = 0.85. Most phasic RSWA burst durations were ≤1.0 s (85th percentiles: SM = 1.07, AT = 0.86 seconds). Older men had significantly higher AT RSWA than older women and younger patients (all p < 0.04). Twenty-nine (25%, 18 men) had RSWA exceeding the cohort 95th percentile, while 17 (14%, 12 men) fulfilled diagnostic cutoffs for phasic or automated RBD RSWA thresholds. Conclusions RSWA levels are highest in older men, mirroring the demographic characteristics of RBD, suggesting that older men frequently have altered REM sleep atonia control. These data establish normative adult RSWA values and thresholds for determination of isolated RSWA elevation, potentially aiding RBD diagnosis and discussions concerning incidental RSWA in clinical sleep medicine practice.