Vitamin D Deficiency Linked to Neurologic Disorders

Parkinson Disease

Parkinson disease is another progressive neurodegenerative disease and involves dopaminergic neuronal loss.1 Motor symptoms include bradykinesia, rigidity, tremor, gait disorders, and postural instability.15 Although human studies examining the relationship between vitamin D and PD have shown inconsistent and often conflicting findings, one of the most consistent findings is an inverse relationship between vitamin D levels and severity of motor symptoms.15 Other consistent findings are that serum levels of vitamin D are significantly lower in patients with overt PD than in patients without PD, and that serum vitamin D levels progressively decrease with increasing severity of PD.16,17 However, it is unclear whether these associations are linked to reduced mobility and decreased sun exposure as Parkinson disease progresses.15

Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis is a fatal disease of neurodegeneration, with a prognosis of a 3- to 5-year life expectancy after diagnosis.18 The disease is characterized by a progressive loss of motor neurons and is linked to glutamate neurotransmitter abnormalities.18 Although several proteins linking vitamin D to ALS pathology have been identified in genetic studies, evidence supporting a causative role is weak.18,19

In a systematic review and meta-analysis of 24 studies, Lanznaster et al found that ALS patients had slightly lower levels of vitamin D than healthy patients in the control group but could not find evidence supporting the role of vitamin D on ALS diagnosis, prognosis, or treatment.”18 Key limitations of studies on this topic are a lack of consideration of confounding factors.18


Establishing a clinical correlation between vitamin D deficiency and neurologic disorders is difficult given the lack of longitudinal randomized controlled trials. It is unclear whether low vitamin D levels found in patients with these disorders are causative or are the result of confounding factors linked to underlying disease processes and associated disability.20 However, current evidence supports a link between MS and areas with higher rates of vitamin D deficiency, and the use of vitamin D supplementation to help slow cognitive decline in AD and reduce PD symptom severity.1,3

Researchers point to the need for rigorous clinical studies on vitamin D supplementation targeting disease-relevant endpoints. For disorders that do show improvement with vitamin D supplementation, alleviating symptoms or reducing the severity or disease expression can provide improvement in patient comfort and outcomes. Thus, treating vitamin D deficiency in patients with neurocognitive disorders to an endpoint of 50 ng/mL may be considered.1

Dana S. Miles, MS, PA-C, CAQ-EM, has been working in emergency medicine as a PA since 2005 and is currently in the Doctor of Medical Science (DMSc) program at A.T. Still University-Arizona School of Health Sciences.

This article originally appeared on Clinical Advisor


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