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Low vitamin D levels linked to doubling in dementia risk

Findings likely to add to debate over role of vitamin in staving off other illnesses

Caroline White

Thursday, 07 August 2014

Elderly people with very low blood levels of vitamin D run double the risk of developing dementia and Alzheimer’s disease, reveals research* published online in the journal Neurology.

The researchers base their findings on 1,658 elderly US adults taking part in the population based Cardiovascular Health Study between 1992-3 and 1999.

Blood samples were taken to check for vitamin D levels in 1999 and their subsequent cardiovascular and cognitive health was tracked for around 5.5 years.

The number of new cases of dementia and Alzheimer’s disease arising during that period was assessed using National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer’s Disease and Related Disorders Association criteria.

In all, 171 people developed dementia, 102 of which were Alzheimer’s disease. A link was found for those with low levels of circulating vitamin D.

Those who were severely vitamin D deficient (less than 25 mmol/l) were around twice as likely to develop dementia from any cause, while those who were moderately deficient (less than 50 mmol/l) were 53% more likely to do so, compared with people with adequate circulating levels of the vitamin.

The authors conclude that their results add to the ongoing debate about the role of vitamin D in health conditions other than osteoporosis.

Commenting on the study, Gordon Wilcock, Emeritus Professor of Geratology, Nuffield Department of Clinical Neurosciences, University of Oxford, said that the findings confirmed those of previous research suggesting a link between vitamin D levels and the risk of dementia.

“It emphasises the need for treatment trials in people with low levels of vitamin D to see if supplements could prevent or delay the onset of dementia, or improve memory function after it has deteriorated,” he suggested.

“One could make a case for checking vitamin D levels in older people who have a poor diet, or who have little exposure to the sun, or alternatively as a part of an older persons’ routine screening programme, because vitamin D is important for other health reasons as well as memory problems and dementia,” he said.

“Dementia is such a devastating disease that preventing or slowing down its progression, if this proves possible with vitamin D supplements, would be extremely important even if the number of people who benefited seems small,” he said.

But Dr Simon Ridley, Head of Research at Alzheimer’s Research UK, the UK’s leading dementia research charity, cautioned: “This interesting study has strengthened the evidence for an association between vitamin D levels and risk of dementia, but it’s not possible to know from this research whether low vitamin D levels could cause dementia.”

And he added: “With the numbers of people with dementia set to increase, it’s vital to continue investing in research to understand the factors that can affect our risk of the condition. In the meantime, there are a number of ways people can lower their risk of dementia, including eating a healthy, balanced diet, exercising regularly, not smoking or drinking too much, and keeping blood pressure and weight in check.”

* Littlejohns T L, et al. Vitamin D and the risk of dementia and Alzheimer disease. Neurology. August 6, 2014, doi: 10.1212/WNL.0000000000000755

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