Alzheimer’s disease is a form of dementia, and its cause is likely to be ‘multifactorial’ and even vary considerably between individuals. However, on thing that appears to be true is that a key driving process in the condition is inflammation (which, by the way, seems to be true for ‘chronic’ conditions). One potential anti-inflammatory agent is vitamin D, and I was interested to read about a recent study which found significant links between low vitamin D levels and risk of developing Alzheimer’s disease and dementia in general.
In short, what this study found is that in those deemed to be low in vitamin D (levels < 50 nmol/l), risk of Alzheimer’s and dementia were raised by 69 and 53 per cent respectively. In those deemed ‘severely deficient’ (levels 25 - < 50 nmol/l) risks were elevated by 122 and 125 per cent respectively. Analysis of the data revealed that there is some sort of threshold below which risk of dementia and Alzheimer’s increases markedly, and that threshold is around 50 nmol/l.
This research is ‘epidemiological’ in nature, and cannot be used therefore to infer that vitamin D helps prevent dementia. It could be, for instance, that those prone to dementia are less likely to get outside in the sun, and are prone to lower vitamin D levels as a result.
However, in this study, people were followed over a period of time (an average of about 5½ years), at the start of which no-one had dementia. In this context, the increasing risk of dementia over time seen in those low in vitamin D points a bit in the direction that the link might be causal (i.e. that vitamin D deficiency might actually provoke dementia). Interestingly, vitamin D has been found to counter specific mechanisms that have been implicated in the development of Alzheimer’s disease .
I think it’s too soon to draw and conclusions about the role of sunlight and vitamin D in dementia. However, I’d say this is ‘one to watch’. If it should turn out that optimising vitamin D levels has benefits for the ageing brain, I don’t think I’ll be too surprised.
1. Littlejohns TJ, et al. Vitamin D and the risk of dementia and Alzheimer disease. Neurology. 2014 Aug 6 [Epub ahead of print]
2. Dursun E, et al. A new mechanism for amyloid-β induction of iNOS: vitamin D-VDR pathway disruption. J Alzheimers Dis. 2013;36(3):459-74