A multiethnic longitudinal cohort study was done in an outpatient clinic including over 300 participants over an 8 year time period. Baseline serum 25-hydroxyvitamin D (25-OHD) was collected and participants were categorized as either deficient, insufficient, adequate, high, or higher based on their levels. Then, neuropsychological assessment scales were used to evaluate cognitive decline.
Following this 8 year period those participants who were classified in the insufficient or deficient in vitamin D showed greater cognitive decline in episodic memory and executive function compared to those in the sufficient and higher categories.
The importance of this research suggests that low vitamin D levels are associated with increased cognitive decline. Although it does not show that vitamin D supplementation slows the progression of cognitive decline it could suggest the important of future research in this area. As vitamin D already is know to exert many other health benefits this could simply be one more area in which vitamin D supplementation is beneficial.