Restless leg syndrome (RLS) is a common sensorimotor disorder characterised by discomfort during rest and the urge to move the limbs, accompanied by abnormal sensations. It is well known that, together with genetic factors, brain iron dysregulation and dopaminergic dysfunction play a role in the pathogenesis of RLS. As vitamin D affects the nigrostriatal dopaminergic pathway, it has been suggested that it could be involved in RLS pathogenesis. In this study, we aimed to investigate vitamin D levels in RLS patients and matched controls.
A total of 107 RLS patients and 107 age and sex-matched healthy controls were included. All RLS patients underwent a structured interview and were clinically evaluated using different RLS severity scales (International RLS rating scale [IRLS], RLS-6, and Clinical Global Impression [CGI]). All patients and controls underwent laboratory examination, including vitamin D analysis. Vitamin D deficiency was present in 8.4% (n=9) of RLS patients as compared to 0.9% (n=1) of controls (p=0.021). In patients with RLS, vitamin D deficiency correlated weakly with all severity scales used (RLS-6: r=0.199; p=0.040; IRLS: r=0.214; p=0.027; CGI: r=0.276; p=0.004). After stratification for early or late onset RLS, patients with late onset RLS were found to display a moderate correlation between both IRLS and CGI and vitamin D deficiency (IRLS: r=0.391; p=0.027, and CGI: r=0.405; p=0.021).
In addition to the known influence of iron parameters on RLS symptoms, the results of this study corroborated the association between vitamin D deficiency and RLS. The correlation between vitamin D deficiency and RLS symptom severity, which was stronger in patients with late onset RLS, suggests that vitamin D deficiency interacts with RLS symptoms. As only a small percentage of RLS patients in our cohort had vitamin D deficiency, the role of vitamin D in RLS pathogenesis needs to be further investigated in future studies.