Seasonality of restless legs syndrome: symptom variability in winter and summer times

Introduction: Restless legs syndrome (RLS) is a common sensorimotor neurological disorder, with symptoms that might cause sleep fragmentation leading to excessive daytime sleepiness. A seasonality of RLS symptoms has been suggested; however, to date, no study focused on this aspect. In order to detect a possible seasonality of RLS manifestations, we evaluated RLS symptom severity and excessive daytime sleepiness in winter and summer in RLS patients. Methods: RLS patients who performed two follow-up visits in summer and winter were included in this retrospective bicentric analysis. RLS severity, measured with the International RLS Study Group rating scale (IRLS), and daytime sleepiness, measured with the Epworth Sleepiness Scale (ESS), were recorded in both seasons in Innsbruck and Rome Sleep Medicine Centers. Results: In sum, 64 RLS patients were included. In the overall sample, IRLS in summer was higher than in winter (p = 0.008). After gender stratification, this held true only in men (p = 0.008). When stratifying for centers, the seasonal variation in RLS severity was present exclusively in Rome (p < 0.001). Moreover, 20 RLS patients completed ESS in both seasonal periods, and scores in summer were higher than in winter (p < 0.001). Conclusion: This retrospective observational study showed an increase of RLS severity during summer compared to winter, supporting the hypothesis that RLS symptoms are more troublesome when temperatures are higher. Changes in microvascular regulation, sweating, and serum iron level changes may support this difference in RLS symptoms across the year. The documented seasonal variation in RLS severity with worsening in the warmer months needs to be investigated further in prospective studies.