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Vitamin D Deficiency Linked to Increased Alzheimer’s Risk

Subjects with severe deficiency show more than two-fold risk increase

Vitamin D deficiency is associated with a substantially higher risk of dementia and Alzheimer’s disease (AD) in older people, according to a new study from Florida International University.

Study participants who had severe vitamin D deficiency were more than twice as likely to develop the disorders compared with subjects with normal vitamin D levels.

The findings were published online August 6 in Neurology.

The researchers evaluated 1,658 elderly ambulatory adults free from dementia, cardiovascular disease, and stroke who participated in the U.S. population–based Cardiovascular Health Study. Serum 25-hydroxyvitamin D (25[OH]D) concentrations were determined by liquid chromatography-tandem mass spectrometry from blood samples collected in 1992—1993.

The investigators found that, during a mean follow-up period of 5.6 years, 171 subjects developed all-cause dementia, including 102 cases of AD.

The multivariate adjusted hazard ratios for incident all-cause dementia in subjects who were severely 25(OH)D deficient (< 25 nmol/L) or deficient (≥ 25 to < 50 nmol/L) were 2.25 and 1.53, respectively, compared with subjects with sufficient concentrations (≥ 50 nmol/L).

Similarly, the multivariate adjusted hazard ratios for incident AD in subjects who were severely 25(OH)D deficient or deficient were 2.22 and 1.69, respectively, compared with subjects with sufficient concentrations. The risk of all-cause dementia and AD markedly increased below a 25(OH)D threshold of 50 nmol/L.

“Emerging evidence shows that vitamin D may contribute to health benefits beyond bone health. This study documented a clear association of vitamin D levels with cognition in older adults,” said lead investigator Dr. Paulo Chaves. “Study results raise the important question regarding whether having proper vitamin D levels could help reduce the risk of dementia. Additional studies are needed to conclusively prove this.”

An estimated 44 million people have dementia worldwide, and this number is expected to triple by 2050. Moreover, an estimated 1 billion people have low vitamin D levels, which puts them at greater risk for health problems.

Sources: Florida International University; August 7, 2014; and Neurology; August 6, 2014.

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