Vitamin D deficiency is associated with decreased cognition independent from the disease status and AD morphology

Abstract

AbstractBackground25(OH)D deficiency was associated with cognitive impairment and altered brain volumes, namely reduction in white matter and medial temporal lobe and enlargement of lateral ventricles. 25(OH)D deficiency was also associated with the development of Alzheimer's disease (AD). In this study, we aimed to investigate whether 25(OH)D levels are independently associated with cognitive performance and AD‐associated morphology in a mixed sample.MethodThe study was conducted at Hacettepe University Faculty of Medicine, Ankara, Turkey. The participants were chosen from our dementia research database.Demographic variables, 25(OH)D levels, standardized Modified Mini Mental Test (3MS) z‐scores, 1.5 T brain MRI, the data for comorbid medical conditions and current prescription drugs were used as pertinent variables. FreeSurfer v.6.0 was used for automated structural neuroimaging analysis. Based on the previous literature, AD cortical signature, predictive cortical thickness, medial temporal lobe gray matter and mean hippocampal volumes were calculated and used independently to assess AD‐related morphological changes. Cut‐off for 25(OH)D deficiency was accepted as 20 ng/ml. Statistical analyses were conducted using IBM SPSS Statistics 23 for Windows. To assess the predictive power of 25(OH)D, regression models were used with standardized 3MS scores and AD‐related areas as dependent variables. Statistical assumptions were met for all models presented. Funded by TUBITAK 214S048 and Hacettepe University THD 2018‐17363.ResultA total of 210 patients over 55 years of age (47 AD, 15 nonAD dementia, 74 Mild and Subjective Cognitive Impairment, 74 cognitively intact) were included. Mean 25(OH) level was 22.48 ±15.8 ng/ml. 108 participants (51.4%) had 25(OH)D deficiency (AD 57%, nonAD Dementia 60%, SCI/MCI 51%, Control 46%, p>0.5). 25(OH)D deficiency was significantly associated with 3MS scores (χ2 =5.608,df=1,p=0.018). The association was also marginally significant when adjusted for age, diagnosis and medial temporal lobe gray matter volume (Exp(β): 2.472, p=0.05). 25(OH)D levels were not associated with AD‐related morphological changes on multivariate analyses.ConclusionPlasma 25(OH)D levels are associated with cognitive performance regardless of the diagnosis. The effect seems to be independent of AD‐related brain morphological changes. Our results suggest an independent effect of 25(OH)D levels on cognition.