NEW ORLEANS—Vitamin D may modulate the course of neurologic diseases such as Alzheimer’s disease and amyotrophic lateral sclerosis (ALS), according to two studies presented at the 64th Annual Meeting of the American Academy of Neurology. Vitamin D deficiency may increase cognitive decline associated with Alzheimer’s disease, and vitamin D supplements could provide benefits for patients with Alzheimer’s disease or ALS, researchers reported.
Previous research has suggested that vitamin D protects the nerves in various ways. Vitamin D simultaneously targets factors that lead to neurodegeneration, including immunoregulatory, antioxidant, and anti-ischemic factors; neurotrophic factors; and acetylcholine neurotransmitters. Vitamin D also helps to clear amyloid-β peptide and to prevent hyperparathyroidism.
Vitamin D and Alzheimer’s Disease
Amie Peterson, MD, a neurologist at Oregon Health and Science University in Portland, and colleagues tested plasma vitamin D levels in 40 nondemented subjects to determine whether vitamin D status predicted cognitive function or CSF biomarker findings in persons at risk of Alzheimer’s disease. All participants (26 women) were older than 60 (mean age, 71) and had first-degree relatives with Alzheimer’s disease. Subjects donated CSF for biomarker studies and underwent cognitive testing, including Mini-Mental State Examination (MMSE) and digit span.
Four of the 40 subjects had sufficient plasma vitamin D concentrations (>40 ng/mL). Seventeen participants were deficient in vitamin D (<30 ng/mL), and 19 had insufficient vitamin D (30 to 40 ng/mL). Plasma vitamin D levels were inversely correlated with age. After adjusting for age, Dr. Peterson’s group found that vitamin D levels were correlated with MMSE score and Backward Digit-Span Task score. Plasma vitamin D, however, was not correlated with CSF amyloid-β1-42, tau, or phosphorylated tau levels.
Vitamin D levels decline with age, and although they might modulate age-related cognitive decline, “reverse causation is also a possibility,” said Dr. Peterson. A vitamin D intervention trial could test this hypothesis.
Vitamin D Associated With Reduction in Cognitive Decline
A separate study found that the highest level of vitamin D intake (ie, 382.1 to 1,774 IU per day) was associated with a 25% reduction in cognitive decline, after adjusting for age, race, income, education, and BMI. Intake of 53.11 to 382 IU per day was associated with an approximately 20% reduction in cognitive decline.
Suzanne E. Judd, PhD, Research Assistant Professor of Biostatistics at the University of Alabama in Birmingham, and colleagues prospectively analyzed data from the Reasons for Geographic and Racial Differences in Stroke Study, which included 30,239 participants age 45 and older. Participants took part in an initial phone interview followed by an in-home examination. A total of 21,437 participants also responded to a Food Frequency Questionnaire, which provided data on nutrition. Approximately 40% of participants were black, and 44% were male. Mean age was approximately 65.
In addition to the reduction in cognitive decline, the highest intake of vitamin D was associated with a 13% reduction in stroke. Intake of 53.11 to 382 IU per day was associated with an approximately 9% reduction of stroke.
“These results suggest an important role for vitamin D in neurologic function,” said Dr. Judd. “However, since this association could be due to unmeasured confounders, and we do not have a good measure of vitamin D status, next steps would be to determine if vitamin D repletion would improve cognitive function and reduce the risk of stroke,” she concluded.
Vitamin D and ALS
Chafic Karam, a fellow at the Mayo Clinic in Rochester, Minnesota, and colleagues studied whether vitamin D supplementation affected the revised ALS Functional Rating Scale (ALSFRS-R) score in patients with ALS. Twenty patients with ALS received 2,000 IU of vitamin D per day for 12 months, and a demographically matched control group of 17 ALS patients did not receive vitamin D. The investigators examined changes in the two groups’ ALSFRS-R scores nine months before the treatment group received vitamin D to ensure that the groups had similar progression. Patients were examined every three months.
Changes in ALSFRS-R scores were similar between the two groups during the initial nine-month period. However, patients who received vitamin D supplements had a slower decline in scores at three, six, and nine months after treatment initiation. The difference between the two groups was not observed at 12 months, and the smaller number of patients available for follow-up at that time might have influenced this result, according to the authors. The greater decline in ALSFRS-R score among patients not taking vitamin D remained after data were adjusted for age and baseline vitamin D level.
—Katherine Wandersee and Erik Greb
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