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. 2021 May 1;17(5):1051-1056.
doi: 10.5664/jcsm.9136.

The seasonal pattern of restless legs syndrome in a sample from the Korean Health Insurance Review and Assessment Service national database

Seong Min Oh  1 , Kyung-Lak Son  1 , Seok-Jin Choi  2 , Mi Hyun Lee  3 , So Young Yoon  3 , Yu Jin Lee  3
Affiliations

The seasonal pattern of restless legs syndrome in a sample from the Korean Health Insurance Review and Assessment Service national database

Seong Min Oh et al. J Clin Sleep Med. .

Abstract

Study objectives: To assess the seasonality of restless legs syndrome (RLS) using data from the Korean national health insurance database.

Methods: We retrospectively reviewed a randomly selected sample representing 3% of the national health insurance claims database in South Korea. From this sample, we obtained the monthly numbers of patients with RLS and diagnoses from 2009 to 2016, along with prescriptions for monthly dopamine agonists and clonazepam for patients with RLS from 2009 to 2013. Total dopamine agonist and clonazepam doses were converted to levodopa-equivalent doses, and the monthly cumulative prescription dose was calculated. Cosinor analysis was used to evaluate the seasonal pattern of each variable.

Results: This study included 11,466 patients with RLS and their diagnoses and 4,887 prescriptions for dopamine agonists and clonazepam. There were significant seasonal patterns in the numbers of patients with RLS (P < .001) and diagnoses (P < .001), both of which peaked in August. The magnitude of the greatest difference in the number of patients with RLS between August (highest) and February (lowest) was 29.96% (95% confidence interval, 24.03-100.80), and that of the number of RLS diagnoses was 39.56% (95% confidence interval, 31.24-47.89). The cumulative prescription dose of medication showed no significant seasonality.

Conclusions: Our findings suggest that the prevalence of RLS is seasonally affected, with an increase during summer.

Keywords: South Korea; Willis-Ekbom disease; national health insurance; restless legs syndrome; seasonality.

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Conflict of interest statement

All authors have seen and approved the manuscript. Work for this study was performed in the Department of Psychiatry, Dongguk University Ilsan Hospital, Goyang, Republic of Korea. The authors report no conflicts of interest.

Figures

Figure 1
Figure 1. Flow diagram of patient selection for analysis of number of patients with RLS diagnoses.
RLS = restless legs syndrome.
Figure 2
Figure 2. Seasonal pattern of the normalized number of patients with RLS in South Korea.
Lines indicate fitted cosinor analysis model. Points with bars are monthly means ± SE. Patients with RLS showed significant seasonality with peaks (A) in August for all (men and women: n = 11,466, amplitude 24.93, phase 8.1, P < .001), (B) in July for men (n = 4,465, amplitude 9.43, phase 7.9, P < .001), and (C) in August for women (n = 7,001, amplitude 15.57, phase 8.2, P < .001). RLS = restless legs syndrome, SE = standard error.
Figure 3
Figure 3. Seasonal pattern of the normalized number of RLS diagnoses in South Korea.
Lines indicate fitted cosinor analysis model. Points with bars are monthly means ± SE. RLS diagnoses showed significant seasonality with peaks (A) in August for all (men and women: n = 11,466, amplitude 124.08, phase 8.0, P < .001), (B) in July for men (n = 4,465, amplitude 45.42, phase 7.9, P < .001), and (C) in August for women (n = 7,001, amplitude 45.42, phase 7.9, P < .001). RLS = restless legs syndrome, SE = standard error.
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