Objective: Aim of this study was to investigate the influence of altitude on periodic leg movements during sleep (PLMS) in subjects with and without restless legs syndrome (RLS).

Background: Peripheral tissue hypoxia has been associated with RLS symptoms and is correlated with RLS severity. Moreover, a higher RLS prevalence was reported in high altitude mountainous regions compared to coastal regions.

Methods: Five untreated RLS individuals and five healthy controls underwent two nights polysomnography according to AASM criteria with additional pCO2 measurements: one night in simulated high altitude environment with normobaric hypoxia corresponding to 3000m above sea level, and a control night at Innsbruck local altitude (574m), in randomized order. PLM scoring was performed twice: according to AASM criteria, and including also respiratory-related leg movements (RRLM).

Results: Five patients (4 f, 1 m) and five controls (3 f, 2 m) participated, mean age 39.7 ± 13.2 years. Age and sex distributions were not different between both groups (p = 0.433 and p = 0.545, respectively). One control and one RLS subject with excessive respiratory events (apnea-hypopnea index, AHI, > 50 /h) at 3000 m were excluded because of the influence of high AHI on PLM count. PLMS index including RRLM differed significantly between the two conditions (8.9 ± 12.1 / h at 574 m, 15.2 ± 12.4 / h at 3000 m; p = 0.042).

Conclusions: This pilot study investigated the acute effect of high altitude on PLMS in individuals with and without RLS. PLMS indices increased at high altitude in both RLS patients and healthy subjects, supporting the pathophysiological role of peripheral hypoxia in RLS. Further studies with larger sample size are needed.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/influence-of-high-altitude-on-periodic-leg-movements-during-sleep-in-individuals-with-restless-legs-syndrome-and-healthy-controls-a-pilot-study/