Evaluation of cognitive subdomains, 25-hydroxyvitamin D, and 1,25-dihydroxyvitamin D in the European Male Ageing Study.

Abstract

Although lower levels of vitamin D have been related to poor cognitive functioning and dementia in older adults, evidence from longitudinal investigations is inconsistent. The objective of this study was to determine whether 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)2D] levels are associated with specified measures of cognitive decline in ageing men. The European Male Ageing Study (EMAS) followed 3369 men aged 40-79 over 4.4years. 25(OH)D levels at baseline were measured by radioimmunoassay, and 1,25(OH)2D levels were obtained with liquid chromatography-tandem mass spectrometry. Visuoconstructional abilities, visual memory, and processing speed at baseline and follow-up were assessed using the Rey-Osterrieth Complex Figure Test (ROCF), Camden Topographical Recognition Memory (CTRM), and the Digit Symbol Substitution Test (DSST). Following attritions, a total of 2430 men with a mean (SD) age of 59.0 (10.6) were included in the analyses. At baseline, the mean 25(OH)D concentration was 64.6 (31.5) nmol/l, and mean 1,25(OH)2D level was 59.6 (16.6)pmol/l. In age-adjusted linear regression models, high 25(OH)D concentrations were associated with a smaller decline in the DSST (β=0.007, p=0.020). Men with low 25(OH)D levels (<50nmol/l) showed a greater decline in the CTRM compared to men with higher (≥75nmol/l) levels (β=-0.41, p=0.035). However, these associations disappeared after adjusting for confounders such as depressive symptoms, BMI, and comorbidities. There was no indication of a relationship between 1,25(OH)2D and decline in cognitive subdomains. We found no evidence for an independent association between 25(OH)D or 1,25(OH)2D levels and visuoconstructional abilities, visual memory, or processing speed over on average 4.4years in this sample of middle-aged and elderly European men.