Limited sunlight may be a risk factor for dementia

People living in northern latitudes may have an increased risk of developing dementia due to the reduced ability to make vitamin D from the limited sunlight suggests a new UK study.

In the observational study, the researchers analyzed data on 65,277 individuals from the Swedish Twin Registry and the Scottish Mental Survey to investigate a potential link between the latitude of residence and the risk of developing dementia (1). The data showed a 2 to 3 fold increased risk of developing dementia among twins born in northern Sweden compared to the more sunny southern Sweden. Among Scottish adults, a similar relationship as that seen in the Swedish twins was seen.

The scientists commented that the higher risk and prevalence of certain diseases such as dementia seen in those living at a northern latitude with limited sunlight may be due to the reduced ability to get a sufficient vitamin D supply from the sunlight induced body own vitamin production in these regions. Further work is required to confirm these findings and identify any potentially modifiable socio-environmental risk factors for dementia responsible for this geographical variation in risk. However, if these factors do exist and could be optimized in the whole population, dementia risk could be significantly reduced, the researchers said.

1. Russ T. et al. Geographical Variation in Dementia: Examining the Role of Environmental Factors in Sweden and Scotland. Epidemiology. Published online January 2015.