Vitamin D and changes in cognitive performance in mid and later life: findings from the English Longitudinal Study of Ageing (ELSA)

Background Vitamin D has been found to be protective against biological processes associated with Alzheimer’s disease and cognition, including amyloid-β deposition, but the evidence in relation to cognitive decline is scarce. Objective This study aims to investigate the relationship between 25(OH)D serum levels and changes in cognitive performance over time in middle-aged and older English adults. Research Design and Methods An observational study design. We analyzed data collected biannually over a 6-year follow-up from a prospective cohort, the English Longitudinal Study of Ageing (ELSA). Mixed Linear Models analyses were conducted. The analytical sample consisted of 5,365 participants aged 50 and older without a diagnosis of dementia at baseline. Cognitive performance was ascertained with memory and orientation. Both tests were administered at every ELSA wave from Wave 6 (2012-2013) to Wave 9 (2018-2019). The values of blood levels of 25(OH)D and all covariates were considered at Wave 6 since this was the first time 25(OH)D was assessed. Blood levels of 25(OH)D were dichotomized in high versus low using the common threshold of 31nmol/l. Results A significant positive association was found between low serum levels of 25(OH)D and baseline memory scores (β= -0.28, SE=0.05, p≤0.001), but not with changes in memory over time. Furthermore, baseline blood levels of 25(OH)D were not associated with baseline orientation or changes in orientation over time. Discussion In this representative sample of the English population, we found that lower 25(OH)D serum levels were associated with a lower baseline memory but did not influence the change in cognitive functioning over time. Implications This study provides further clarification in understanding the deficient role of 25(OH)D on cognitive performance and the change in cognitive functioning over time.