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Background: The prevalence of restless legs syndrome (RLS) in patients with peripheral neuropathy has been reported to be higher than that of the general population in some studies, which suggests an association between neuropathy and RLS, but not all studies show increased RLS with neuropathy. These differences may reflect adequacy of the diagnosis, effects of chronic pain complicating the diagnosis, or population differences. Moreover, if there is increased risk for RLS with neuropathy, it may reflect consequences of the chronic pain rather than other aspects of diabetes mellitus (DM). Therefore, we investigated the effects of diagnosis rigor on the estimated prevalence of RLS in patients with diabetic peripheral neuropathy (DPN) and those with chronic leg pain from osteoarthritis (OA), and then we compared the RLS prevalence in these two populations with each other and with population prevalence for Korea., Methods: Our study is a prospective case-control study of 199 patients with DPN and 220 patients with OA. After evaluating the presence of RLS in these subjects using the diagnostic criteria of the International RLS Study Group, we confirmed the diagnosis of RLS through face-to-face interviews using the 18-item Hopkins Diagnostic Questionnaire, which removes RLS mimics; and through independent examinations by two neurologists., Results: Of the 199 subjects with DPN, 44 (22%) appeared to have RLS from their answers on the 4-item RLS diagnostic questionnaire compared to 8 (3.6%) of 220 subjects with OA. However, the prevalence of RLS in the DPN group dropped to 16 (8%) subjects but stayed at 8 (3.6%) OA subjects when using the Hopkins Telephone Diagnostic Interview (HTDI) adapted for clinical interview. The RLS prevalence determined by HTDI remained significantly higher (P=.042) in the DPN group compared to the OA group and was twice that reported for the general Korean population (8% vs 3.9%). Among subjects with DPN, those with RLS were older (68.06±8.43years vs 62.46±11.05years; P=.049) and had higher pain scores (visual analog scale [VAS], 4.69±2.52 vs 2.72±2.12; P=.002). The quality of sleep (MOS [Medical Outcomes Study] sleep scale) and health-related quality of life (QoL) (total score on the 36-Item Short-Form Health Survey [SF-36]) showed no significant difference between the two groups., Conclusions: The prevalence of RLS in patients with DPN cannot be accurately assessed with only the four diagnostic criteria interview, but the prevalence was higher than expected for Koreans from the general population prevalence and also was higher than occurred with OA patients with chronic leg pains when accurately assessed with a structured interview. Chronic leg pain from OA does not significantly complicate RLS diagnosis, and chronic pain itself does not explain the increased RLS prevalence in diabetic neuropathy., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Study Objectives: Recent genome-wide association studies (GWAS) for Caucasians identified several allelic variants associated with increased risk of developing restless legs syndrome (RLS), also known as Willis-Ekbom disease. Although the pathogenic mechanisms of RLS are not entirely understood, it is becoming increasingly evident that many diseases such as RLS can be attributed to an epistasis. The study objectives were to evaluate whether the associations of RLS with all loci determined in previous GWAS for Caucasians can be replicated significantly for the Korean population and to elucidate whether an epistasis plays a role in the pathogenesis of RLS., Design Setting and Participants: DNA from 320 patients with RLS and 320 age- and sex-matched controls were genotyped for variants in the RLS loci., Measurements and Results: A significant association was found for rs3923809 and rs9296249 in BTBD9 (P < 0.0001 and P = 0.001, respectively); the odds ratio (OR) for rs3923809 was 1.61 (P < 0.0001) to 1.88 (P < 0.0001) and the OR for rs9296249 was 1.44 (P = 0.001) to 1.73 (P = 0.002), according to the model of inheritance. The OR for the interaction between rs3923809 in BTBD9 and rs4626664 in PTPRD was 2.05 (P < 0.0001) in the additive model, 1.80 (P = 0.002) in the dominant model and 2.47 (P = 0.004) in the recessive model. There was no significant association between genotypes of all tested single nucleotide polymorphisms and the mean value of serum iron parameters., Conclusions: Our results suggest that the role of BTBD9 in the pathogenesis of restless legs syndrome is more universal across populations than previously reported and more efforts should be focused on the role of epistasis in the genetic architecture of restless legs syndrome.

Background: There have been few quality of life (QoL) studies of patients with restless legs syndrome (RLS) in Asian countries. We studied the QoL of patients with RLS and compared it to normal controls and patients with hypertension, type 2 diabetes, or osteoarthritis in Korea., Methods: A total of 215 RLS patients (141 female; mean age 51.7 ± 13.5) were enrolled. All patients completed the questionnaires, including all the Korean versions of SF-36, RLS QoL, the International RLS Severity scale (IRLS), the Pittsburgh Sleep Quality Index (PSQI), and the Beck Depression Inventory-2 (BDI-2). These results were compared with the scores from normal controls (N=214) and from patients with hypertension (196), uncomplicated type 2 diabetes (185), or osteoarthritis of the knee (177)., Results: The SF-36 QoL in patients with RLS was lower than that of the normal controls, and even lower than patients with hypertension or diabetes, but higher than those with osteoarthritis. The SF-36 Qol of RLS patients showed a significantly negative correlation with the severity of RLS symptoms(r=-0.430, p<0.001) and the severity of depression (r=-0.565, p<0.001), but was not significantly related to gender, age, or age-of-symptom onset (early or late-onset). Step-wise multiple regression identified three factors related to SF-36 QoL: depression (46.5% of RLS had responses on BDI-2 indicating depression) (β=-.899, p<0.001), RLS symptom severity (K-IRLS) (β=-.718, p<0.001), and gender (female) (β=-6.128, p=0.007)., Conclusions: These findings show that RLS has a considerable impact on the QoL of Koreans, which is comparable with studies of western countries. The QoL impairment relates to the degree of depression with RLS for Koreans., (Copyright © 2012 Elsevier B.V. All rights reserved.)