Vitamin D deficit linked to dementia

World first study from Uni of South Australia finds low levels of vitamin D associated with lower brain volumes and increased risk of dementia and stroke.

The most effective way to get vitamin D is from sun exposure. Picture Lachie Millard

Genetic research has revealed a direct link between ­dementia and a lack of vitamin D.

The world-first study from the University of South Australia investigated the link between vitamin D, neuroimaging features, and the risk of dementia and stroke. It found low levels of vitamin D were associated with lower brain volumes and an ­increased risk of dementia and stroke.

The researchers postulated that in some populations, as many as 17 per cent of dementia cases might be prevented by ­increasing everyone to normal levels of vitamin D.

The scientists undertook genetic analysis to establish that there was a causal effect of vitamin D deficiency and dementia.

Dementia is a chronic or progressive syndrome that leads to deterioration in cognitive function. It is often caused by Alzheimer’s disease. About 487,500 Australians live with dementia and it is the country’s second leading cause of death, with rates expected to increase markedly in coming decades.

The minimum healthy level of vitamin D is 50 nmol/L, but an estimated 31 per cent of adults in Australia have inadequate vitamin D, increasing to more than 50 per cent in women during winter and spring in the southern states.

The UniSA study found that those with vitamin D of only 25 nmol/L had a 54 per cent higher risk of developing ­dementia than those whose ­levels were 50 nmol/L.

The researchers found 17 per cent of dementia cases could be prevented by increasing vitamin D levels from 25 to 50 nmol/L.

The most effective way to get vitamin D is from sun exposure, but many people spend excessive amounts of time indoors or cover up or wear sunscreen when they do go in the sun in line with sun safety messages. Only small amounts of vitamin D can be ­obtained from dietary sources.

It’s recommended that people get around 15 minutes’ sun exposure a day with arms and face exposed, and more if you have darker skin.

The UniSA study analysed data from 294,514 participants from the UK Biobank, examining the impact of low levels of vitamin D (25 nmol/L) and the risk of dementia and stroke.

Senior investigator in the study and director of UniSA’s Australian Centre for Precision Health Elina Hyppönen said the findings had far-reaching implications. She said it would be highly significant if boosting ­levels of vitamin D was able to ­reduce global rates of dementia.

“Vitamin D is a hormone precursor that is increasingly recognised for widespread effects, including on brain health, but until now it has been very difficult to examine what would happen if we were able to prevent vitamin D deficiency,” Professor Hyppönen said.

“Our study is the first to examine the effect of very low levels of vitamin D on the risks of dementia and stroke, using ­robust genetic analyses among a large population … In this UK population, we observed that up to 17 per cent of dementia cases might have been avoided by boosting vitamin D levels to be within a normal range.”

The study has been published in the journal Original Research Communications.