Vitamin D deficiency linked to Alzheimer’s disease

Individuals who have a vitamin D deficiency have a higher risk of developing Alzheimer’s disease, according to a prospective, population-based study published online for Neurology, the journal of the American Academy of Neurology.

Low vitamin D concentrations, defined as deficient (≥25 nmol/L to <50 nmol/L) in adults from the Cardiovascular Health Study, were associated with a 51% increased risk of Alzheimer’s disease and all-cause dementia after follow-up of a mean of 5.6 years (range, 0.1 to 8.4 years). Those with a severe deficit of vitamin D (<25 nmol/L) were at higher risk for Alzheimer’s disease and dementia, reaching more than 120%, the researchers noted.

The Cardiovascular Health Study was a prospective U.S. study that investigated the underlying reasons for cardiovascular disease in older men and women who were enrolled in 1989-1990 and a cohort of African Americans was added in 1992-1993. Dementia and Alzheimer’s disease was assessed in 1998-1999 by neurologists and psychiatrists, with diagnosis based on interviews, questionnaires, MRIs, annual cognitive reviews, and medical records.

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More than 1,650 patients from the Cardiovascular Health Study were enrolled in the vitamin D study and followed for a mean of more than 5 years. At the end of the study, 171 had all-cause dementia and 102 had Alzheimer’s disease. When adjusting for age, season of vitamin D collection, education, sex, body mass index, smoking, alcohol consumption, and depression, 168 cases of all-cause dementia and 100 cases of Alzheimer’s disease resulted.

“The optimal level of vitamin D for general health remains controversial, with the Institute of Medicine recommending 50 nmol/L and the Endocrine Society recommending 75 nmol/L,” the authors noted.

“Our results clarify that the threshold above which older adults are unlikely to benefit from supplementation with regard to dementia risk is likely to lie in the region of 50 nmol/L,” they said.

The authors believe their findings suggest that vitamin D may be neuroprotective and that sufficient vitamin D concentrations should be about 50 nmol/L to maintain general health.