A recent study found that restless legs syndrome is more frequent and more severe in vitamin D deficient individuals. Additionally, vitamin D deficiency was associated with poor sleep quality.
Restless legs syndrome (RLS) is a chronic, progressive neurological disorder characterized by an uncontrollable urge to move one’s legs, usually due to leg discomfort. Moving temporarily relieves the discomfort. RLS often disrupts sleep; about 20% of patients with RLS have sleep disorders.
The cause of RLS is typically unknown. However, researchers believe an imbalance of dopamine likely plays a role. Dopamine is a brain chemical that sends messages to control muscle movement. The most commonly used treatment for RLS is dopamine agonists, which are chemicals that bind to receptors and elicit the production of dopamine.
Research has shown that vitamin D increases the levels of dopamine in the brain and protects the brain from toxins that can cause an imbalance of dopamine levels. This led researchers to suspect that vitamin D may help treat RLS. One pilot study found that vitamin D supplementation improved the severity of RLS. Though, this study only included 12 patients.
Researchers recently conducted a study in 102 patients to assess the link between vitamin D deficiency and the frequency and symptom severity of RLS along with sleep quality in vitamin D deficiency. The researchers evaluated these outcomes in two different groups: those who were vitamin D deficient (levels less than 20 ng/ml) and those who were vitamin D sufficient (levels greater than or equal to 20 ng/ml).
The researchers diagnosed RLS based on the International RLS Study Group (IRLSSG) diagnostic criteria. Individuals were diagnosed with RLS if the patient experienced all of the following symptoms: urge to move the legs, onset of exacerbation with rest, relief with movement and worsened symptoms in the evening. The severity of RLS was assessed with the IRLSSG Symptom Severity Scale. This scale asks questions about the typical symptoms of RLS, each graded 0-4. Higher points indicate a higher severity of the disease. Pittsburgh sleep quality index (PSQI) was used to evaluate sleep quality. The PSQI scores the quality and amount of sleep and the presence and severity of sleep disorders, with a higher score representing worse sleep quality.
The incidence and severity of RLS along with sleep quality were compared between the two groups. Here is what the researchers found:
- The vitamin D deficient group had a significantly higher incidence of RLS compared to the vitamin D sufficient group (p = 0.034).
- The PSQI points were significantly worse in the vitamin D deficient group compared to the vitamin D sufficient group (p < 0.05).
- No significant difference was observed in symptom severity between the two groups.
The researchers concluded,
“…The results of this study demonstrated a relationship between vitamin D and RLS and sleep problems.”
The main limitation of this study is that it does not prove causation. The study does not conclude that vitamin D supplementation improves RLS. Also, the study was not prospective.
Large randomized controlled trials need to be conducted in order to increase the understanding of the effects of vitamin D supplementation on RLS.