Despite this being an observational study, the analysis for extraneous factors has been strong enough that the authors believe the link between vitamin D deficiency and dementia/stroke is causal. As the study itself says, almost 20% of dementia/stroke cases could be prevented by simply supplementing with vitamin D. And since by supplementation such studies often mean using the puny RDA value/dose, that means a daily dose of 2,000 - 3,000 IU may be much more effective and save a much higher percentage of people.
Vitamin D and brain health: an observational and Mendelian randomization study
Vitamin D deficiency can lead to dementia
"...A world-first study from the University of South Australia could make this a reality as new genetic research shows a direct link between dementia and a lack of vitamin D. Investigating the association between vitamin D, neuroimaging features, and the risk of dementia and stroke, the study found:
Vitamin D and brain health: an observational and Mendelian randomization study
Vitamin D deficiency can lead to dementia
"...A world-first study from the University of South Australia could make this a reality as new genetic research shows a direct link between dementia and a lack of vitamin D. Investigating the association between vitamin D, neuroimaging features, and the risk of dementia and stroke, the study found:
- low levels of vitamin D were associated with lower brain volumes and an increased risk of dementia and stroke
- genetic analyses supported a causal effect of vitamin D deficiency and dementia.
- in some populations as much as 17 per cent of dementia cases might be prevented by increasing everyone to normal levels of vitamin D (50 nmol/L).
