A new scientific study published in Neurology from researchers at McGill University has provided evidence to support vitamin D as a causal risk factor for Alzheimer’s disease (AD). The McGill study found that lower vitamin D levels increased the risk of Alzheimer’s disease by 25% using a Mendelian randomization (MR) methodology which minimizes bias due to confounding or reverse causation.
Alzheimer’s disease is expected to double throughout the world in the next 20 years. The Alzheimer Society of Canada estimates that approximately 747,000 Canadians are living with some form of dementia.
There is no treatment that can effectively stop the progression of Alzheimer’s disease despite considerable effort. Therefore, disease prevention through modifiable risk factors where possible is critical. Ensuring vitamin D sufficiency through increased non-burning sun exposure in summer or vitamin D supplementation may be a cost-effective approach to help reduce Alzheimer’s disease risk.
“The strength of the Mendelian randomization (MR) approach is that it examines the genetic determinants of vitamin D status which are less likely to be influenced by confounding and reverse causation,” says first author, Lauren Mokry, MSc, Department of Epidemiology and Biostatistics, McGill University. “I think our paper in combination with the concordant results of meta-analysis offers strong evidence for a positive role of vitamin D in AD etiology.”
The authors concluded: “Our results provide evidence supporting 25OHD (vitamin D) as a causal risk factor for Alzheimer disease (AD). These findings provide further rationale to understand the effect of vitamin D supplementation on cognition and AD risk in randomized controlled trials.”
Evidence that vitamin D plays a role in Alzheimer’s disease risk continues to mount. In 2015, a meta-analysis study was published in Nutrition Journal which showed that subjects with deficient vitamin D status, <50 nmol/L, had a 21% increased risk of developing Alzheimer’s disease compared to people with vitamin D levels > 50 nmol/L.
