Low Vitamin D Levels and Cognitive Impairment

NHANES Findings



Vitamin D was once just of interest in bone health, but recent work has suggested low vitamin D levels may be a risk factor for a wide range of age-associated diseases, Dr. Llewellyn said, including cancer, hypertension, stroke, and more recently, cognitive decline.


It is known that vitamin D crosses the blood–brain barrier and that receptors for vitamin D are found across the brain, but its precise role is still not known, Dr. Llewellyn noted. It does seem to play a role in processes that may be important for dementia risk, including vascular health and amyloid clearance from the brain. Given these associations, he noted, it seems "biologically plausible" that there might be an association of low vitamin D levels with dementia risk and cognitive performance in the general population.


It is estimated that about a billion people worldwide have vitamin D levels considered insufficient (<75 nmol/L). Most of the world's population living in the northern hemisphere does not have sufficient exposure to the sun to produce enough vitamin D, there are few dietary sources, and aging skin loses the ability over time to produce vitamin D. "So it's an enormous public health concern, given its association with an increasingly wide range of age-associated diseases," Dr. Llewellyn said.

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