A recent study published by the Journal of Back and Musculoskeletal Rehabilitation found that vitamin D deficiency is linked with the development and severity of carpal tunnel syndrome.
The carpal tunnel is a channel in the wrist that connects the forearm with the palm. This channel encases bones, tendons and the median nerve. When inflammation and swelling is present in the carpal tunnel, the median nerve may become compressed, resulting in carpal tunnel syndrome (CTS). Those with CTS may experience muscle weakness, pain, numbness and tingling of the thumb side of the hand and forearm.
This condition is the most common form of entrapment neuropathy. Those between the ages of 30 and 50 years are most frequently diagnosed with CTS, and women are three times more likely to develop CTS than men.
Vitamin D has been shown to exert anti-inflammatory properties by inhibiting the production of cytokines, a pro-inflammatory protein. Since CTS is driven by inflammation, researchers hypothesize that vitamin D may play a role in the development of CTS; however, no studies to date have evaluated this relationship.
Therefore, in a new study, researchers aimed to determine whether vitamin D is related to the onset or severity of CTS. A total of 90 patients who were admitted to the Bozok Univeristy Hospital Neurology Clinic and Electromyography (EMG) Laboratory in Yozgat, Turkey with a mild to moderate case of CTS were included in the study. The patients had their BMI calculated and their vitamin D levels measured. The following tools were used to assess the level of neuropathy:
- The Douler Neuropathique 4 Questionnaire was used to assess the symptoms and neuropathic pain level. Scores of at 4 or more suggests the presence of significant pain.
- The Visual Analogue Scale was used to determine the intensity of pain in CTS patients, with a higher score indicating a greater level of pain.
- The electrophysiological evaluation involved the use of nerve conduction techniques to determine the severity of the disease. Mild CTS was classified when patients presented a slow finger-wrist nerve tract with normal motor function at the distal point of the median nerve, moderate CTS was determined in patients with slowed finger-wrist tract with a decreased response from the distal point of the median nerve, while severe CTS was diagnosed in the absence of finger-wrist tract and an increased response from the distal point of the median nerve.
Here is what they found:
- The patient’s vitamin D status was not significantly associated with age, gender or BMI (p > 0.05).
- A total of 67% of the patients with CTS were vitamin D deficient (<10 ng/mL) with a mean 25(OH)D status of 6.83 ng/ml +64 ng/ml (p < 0.001).
- Vitamin D status was inversely associated with CTS severity (p = 0.004).
- Vitamin D deficiency was related to an elevated BMI and neuropathic pain.
The researchers concluded:
“The present study found that the frequency of mild CTS was significantly higher in patients with a vitamin D deficiency than in those without a vitamin D deficiency, and that the severity of the vitamin D deficiency was associated with the severity of CTS in patients with a vitamin D deficiency.”
This is the first study to find a relationship between vitamin D status and CTS. However, the study was limited by its observational design and lack of a control group. Also, none of the patients experienced severe CTS and vitamin D deficiency was highly prevalent which may have decreased the strength of its findings. The Vitamin D Council considers those to be vitamin D deficient when their 25(OH)D status drops below 30 ng/mL. The fact that the researchers utilized a reference range indicating severe deficiency by all standards recognized in the US and still found such a high prevalence, suggests that further research is warranted.
Therefore, large scaled clinical trials are needed to determine if vitamin D may be beneficial in the prevention and treatment of CTS.
Sturges, M. & Cannell, JJ. Vitamin D status linked with carpal tunnel syndrome, according to study. The Vitamin D Council Blog & Newsletter, 2016.