Ethnic differences in periodic limb movements during sleep in patients with restless legs syndrome: a preliminary cross-sectional study of Austrian and Japanese clinical population
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Periodic limb movements during sleep (PLMS) are identified as a common finding in patients with restless legs syndrome (RLS). Although PLMS are observed in more than 80% of RLS patients in Western countries, little is known about Asian RLS patients and no data are available about Japanese patients. This cross-sectional study aimed to investigate ethnic differences in clinical information and polysomnographic variables including PLMS between Austrian and Japanese RLS patient undergoing nocturnal polysomnography (n-PSG). One hundred Austrian and 139 Japanese consecutive patients diagnosed with RLS who underwent n-PSG were included [Austrian 54.5 ± 13.6 years, 40 females (40%); Japanese 50.2 ± 18.9 years, 88 females (63.3%)]. Medical records and n-PSG data were reviewed retrospectively. Epidemiological, clinical and n-PSG variables were compared between the two groups. Rate of patients with PLMS ≥ 5/h and those with PLMS ≥ 15/h were higher in Austrian than in Japanese RLS patients (80.0 vs. 56.1%, P < 0.001; 55.0 vs. 41.7%, P = 0.043). Accordingly, Japanese RLS patients showed lower PLMS index than Austrian patients (21.3 vs. 33.6/h, P = 0.008). Japanese RLS patients showed higher female predominance, lower BMI, lower systolic/diastolic blood pressure, lower ferritin level and higher International restless legs syndrome severity scale than Austrian patients. None of these variables were associated with PLMS in both groups. Japanese RLS patients showed significantly lower comorbidity rate and lower indices of PLMS compared to Austrian RLS patients. This cross-sectional study on ethnic differences in PLMS in patients with RLS may provide a bridge to a future genetic comparative study between European and Asian RLS patients.
KeywordsRestless legs syndrome Ethnic difference Periodic limb movements during sleep Nocturnal polysomnography Blood pressure
This study was funded by a MEXT/JSPS KAKENHI Grant-in-Aid for Young Scientists (No. 15K19499) to Dr. Sasai-Sakuma. We appreciate the participants of this study and medical staff members of the Yoyogi Sleep Disorder Center and of the Sleep Disorders Clinic, Department of Neurology of the Medical University of Innsbruck for their cooperation.
Compliance with ethical standards
Conflict of interest
No authors have conflict of interest about this study.
The Ethical Committee of the Neuropsychiatric Research Institute and the Ethics Committee of the Medical University of Innsbruck reviewed and approved the study protocol, which is in accordance with the Declaration of Helsinki. All the participants provided consent for their medical records to be used in this study.
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