Genome-wide association and whole exome sequencing studies reveal a novel candidate locus for restless legs syndrome

Association between inflammatory cytokines and disease severity in restless legs syndrome

BACKGROUND

This study aims to evaluate serum cytokine levels in individuals with primary Restless Legs Syndrome (RLS) and analyze their correlation with RLS symptom severity, sleep disturbances, anxiety, and depression.

METHODS

A case-control study was conducted involving 87 primary RLS patients and 100 healthy individuals undergoing health check-ups. Serum cytokine levels were assessed, and RLS severity was evaluated using the International Restless Legs Syndrome Study Group (IRLSSG) rating scale. Additionally, the Pittsburgh Sleep Quality Index (PSQI), 24-item Hamilton Depression Rating Scale (HAMD24), and 14-item Hamilton Anxiety Rating Scale (HAMA14) were utilized to assess symptom severity, sleep disturbances, and emotional states in RLS patients.

RESULTS

Serum cytokine levels, including IL-6 and TNF-α, were significantly higher in RLS patients compared to controls (P < 0.05). Adjustment for disease duration, sex, age, BMI, SBP, and DBP revealed an independent association between serum IL-6 and RLS (OR = 1.46; 95% CI = 1.02-1.93; P = 0.003). Linear regression analysis demonstrated a significant correlation between IL-6 levels and IRLS scores (β = 0.123, P = 0.008).

CONCLUSION

Elevated circulating levels of inflammatory cytokines in RLS patients suggest a potential role of inflammation in the pathogenesis of primary RLS. Additionally, serum cytokine levels correlate closely with disease severity.

Putative Animal Models of Restless Legs Syndrome: A Systematic Review and Evaluation of Their Face and Construct Validity

Restless legs syndrome (RLS) is a sensorimotor disorder that severely affects sleep. It is characterized by an urge to move the legs, which is often accompanied by periodic limb movements during sleep. RLS has a high prevalence in the population and is usually a life-long condition. While its origins remain unclear, RLS is initially highly responsive to treatment with dopaminergic agonists that target D2-like receptors, in particular D2 and D3, but the long-term response is often unsatisfactory. Over the years, several putative animal models for RLS have been developed, mainly based on the epidemiological and neurochemical link with iron deficiency, treatment efficacy of D2-like dopaminergic agonists, or genome-wide association studies that identified risk factors in the patient population. Here, we present the first systematic review of putative animal models of RLS, provide information about their face and construct validity, and report their role in deciphering the underlying pathophysiological mechanisms that may cause or contribute to RLS. We propose that identifying the causal links between genetic risk factors, altered organ functions, and changes to molecular pathways in neural circuitry will eventually lead to more effective new treatment options that bypass the side effects of the currently used therapeutics in RLS, especially for long-term therapy.

Polysomnographic nighttime features of Restless Legs Syndrome: A systematic review and meta-analysis

Background

Restless Legs Syndrome (RLS) is a common sleep disorder. Polysomnographic (PSG) studies have been used to explore the night sleep characteristics of RLS, but their relationship with RLS has not been fully analyzed and researched.

Methods

We searched the Cochrane Library electronic literature, PubMed, and EMBASE databases to identify research literature comparing the differences in polysomnography between patients with RLS and healthy controls (HCs).

Results

This review identified 26 studies for meta-analysis. Our research found that the rapid eye movement sleep (REM)%, sleep efficiency (SE)%, total sleep time (TST) min, and N2 were significantly decreased in patients with RLS compared with HCs, while sleep latency (SL) min, stage shifts (SS), awakenings number (AWN), wake time after sleep onset (WASO) min, N1%, rapid eye movement sleep latency (REML), and arousal index (AI) were significantly increased. Additionally, there was no significant difference among N3%, slow wave sleep (SWS)%, and apnea-hypopnea index (AHI).

Conclusion

Our findings demonstrated that architecture and sleep continuity had been disturbed in patients with RLS, which further illustrates the changes in sleep structure in patients with RLS. In addition, further attention to the underlying pathophysiological mechanisms of RLS and its association with neurodegenerative diseases is needed in future studies.

Association between thyroid function and disease severity in restless legs syndrome

Background

Restless Legs Syndrome (RLS) is a common neurological disorder. Growing evidence shows that dopaminergic dysfunction and iron deficiency are associated with the pathogenesis of RLS. Additionally, the dopaminergic system is linked with the hypothalamic-pituitary-thyroid (HPT) axis. Thus, the current study aimed to compare thyroid function between RLS patients and healthy subjects and investigate the associations with clinical characteristics of RLS.

Methods

Serum levels of thyroid hormones were investigated in 102 first-episode drug-naïve RLS patients and 80 matched healthy controls (HCs). Baseline data and clinical characteristics were performed by professional personnel. In addition, multivariate regression was used to analyze the relationship between thyroid function and RLS.

Results

Compared with control group, RLS patients had significantly higher serum thyroid-stimulating hormone (TSH) levels (p < 0.001), and higher prevalence of subclinical hypothyroidism [Odds ratio (OR) 8.00; 95% confidence interval (CI) = 3.50–18.30; p < 0.001]. The Subclinical hypothyroidism rate (47.1 vs. 10%, p < 0.001) in RLS patients was higher than the HCs group. Regression analysis revealed that serum TSH (OR = 1.77; 95% CI = 1.41–2.23; p < 0.001) was independently associated with RLS. There was a statistically significant positive correlation between TSH and the Pittsburgh sleep quality index (PSQI) scores (r = 0.728, p < 0.001), and the International Restless Legs Scales (IRLS) points (r = 0.627, p < 0.001). Spearman correlation analysis showed that FT₃ was positive correlated with HAMA₁₄ score (r = 0.239, p = 0.015). In addition, compared with the good-sleeper group, poor-sleeper patients had significantly higher serum TSH levels (p < 0.001).

Conclusion

Serum levels of TSH and the prevalence of subclinical hypothyroidism were higher in RLS patients, indicating the imbalance between thyroid hormones (TH) and the dopaminergic system may contribute to the development of primary RLS. Additionally, the TH axis may influence the quality of sleep in RLS patients.