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Study validates link between vitamin D and dementia and Alzheimer’s disease

Vitamin D deficiency linked to a considerable greater risk of all-cause

Heart disease and mid-life hypertension increase the risk of Alzheimer’s disease and Vascular dementia.
GettyImages/Peter Dazeley
In a large study adults who were moderately deficient in vitamin D were 53% more likely to develop all-cause dementia and those who were severly deficient had a 125% increased risk.
GettyImages/Dorling Kindersley

More than five million American’s have Alzheimer’s disease which is the sixth leading cause of death in the United States.

An International team led by Dr. David Llewellyn, PhD, Senior Research Fellow in Clinical Epidemiology at the University of Exeter Medical School had set out to deter mine whether low vitamin D concentrations are linked to an increased risk of incident all-cause dementia and Alzheimer’s disease.

The researcher team examined 1,658 ambulatory elderly American adults who were free from dementia, cardiovascular disease and stroke who participated in the US population–based Cardiovascular Health Study between 1992–1993 and 1999 were included.

Serum 25-hydroxyvitamin D (25(OH)D) concentrations were determined by liquid chromatography-tandem mass spectrometry from blood samples collected in 1992–1993 Incident all-cause dementia and Alzheimer disease status were assessed during follow-up using National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer's Disease and Related Disorders Association criteria.

During a mean follow-up of 5.6 years 171 participants developed all-cause dementia, including 102 cases of Alzheimer disease.

Participants in the study who were moderately deficient of vitamin D had a 53% of developing dementia of any kind and for those who were severely deficient of the vitamin had a 125% increased risk.

Participants who were moderately deficient of vitamin D had a 69% more likely chance to develop the most common type of dementia; Alzheimer’s disease and for those who were severely deficient had a 125% increased risk.

The researchers also found evidence that there is a threshold level of Vitamin D circulating in the bloodstream below which the risk of developing dementia and Alzheimer's disease increases which I s below a threshold of 50 nmol/L.

According to Dr. Llewellyn "We expected to find an association between low Vitamin D levels and the risk of dementia and Alzheimer's disease, but the results were surprising -- we actually found that the association was twice as strong as we anticipated.”

"Clinical trials are now needed to establish whether eating foods such as oily fish or taking vitamin D supplements can delay or even prevent the onset of Alzheimer's disease and dementia. We need to be cautious at this early stage and our latest results do not demonstrate that low vitamin D levels cause dementia. That said, our findings are very encouraging, and even if a small number of people could benefit, this would have enormous public health implications given the devastating and costly nature of dementia."

A study conducted by the Rand Corporation last year had found almost 15% of Americans age 71 and older or 3.8 million people have dementia.

Researchers who work on Alzheimer’s diseases were allocated federal money in the sum of $503 billion in the fiscal year of 2012. They also found direct healthcare expense for dementia's were $109 billion in 2010. Each case costs $41,000 to $56,000 a year, the study found. By comparison, direct expenses in the same year for heart disease were $102 billion.

Dr. Michael D. Hurd, PhD, lead author of study and a senior economist at RAND had commented “There are no signs that the costs of dementia will decrease given that the nation will have a larger number of 85-year-olds in the future than we do today,” Hurd said. “Unless there is some sort of medical breakthrough, these costs will continue to rise.”

This research is the first large study to investigate the relationship between vitamin D and dementia risk where the diagnosis was made by an expert multidisciplinary team, using a wide range of information including neuro-imaging.

Vitamin D can be obtained by three main sources; exposure to sunlight, foods high in vitamin D such as fish and fish oil, and supplements.

Dr. Doug Brown, PhD, Director of Research and Development at Alzheimer's Society commented “Shedding light on risk factors for dementia is one of the most important tasks facing today's health researchers. While earlier studies have suggested that a lack of the sunshine vitamin is linked to an increased risk of Alzheimer's disease, this study found that people with very low vitamin D levels were more than twice as likely to develop any kind of dementia.

"During this hottest of summers, hitting the beach for just 15 minutes of sunshine is enough to boost your vitamin D levels. However, we're not quite ready to say that sunlight or vitamin D supplements will reduce your risk of dementia. Large scale clinical trials are needed to determine whether increasing vitamin D levels in those with deficiencies can help prevent the dementia from developing."

This study is published in Neurology.

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