Amyloid Beta Biomarkers and Their Association with Cognitive Impairment Across Vitamin D Strata: A Cross-Sectional Study in an Older Adult South Indian Population.

Introduction: Vitamin D status has been investigated as a modifiable risk factor with cognitive decline. However, studies pertaining to this remain inconsistent across populations, and there are fewer studies associating vitamin D status, cognitive decline, amyloid markers and oxidative stress markers in older adults. Therefore, this study was conducted to analyze the association between these parameters. Methodology: This cross-sectional study included 145 older adults aged between 51 and 80 years. Participants were categorized based on serum vitamin D levels into sufficient (n = 53), insufficient (n = 61), and deficient (n = 31) groups. Cognitive performance was assessed using the Modified Mini Mental State (3MS) test. Plasma levels of Aβ 1-40 and Aβ 1-42 and oxidative stress markers (TBARS, GPx, SOD) were measured. Statistical analysis was performed using ANOVA and Spearman's correlation. Results: Results showed that the vitamin D concentrations did not differ significantly between cognitively impaired and normal individuals within vitamin D strata (vitamin D sufficient, insufficient and deficient groups). Plasma Aβ 1-40 levels were significantly elevated in cognitively impaired participants across all vitamin D groups. A reduced Aβ 1-42/Aβ 1-40 ratio was observed in sufficient and insufficient Vitamin D groups. Additionally, GPx levels were significantly higher in the vitamin D-deficient group. Correlation analysis showed that 3MS scores were negatively associated with age (r = -0.2607, p = 0.0015), Aβ 1-40 (r = -0.4016, p = 0.0001), and Aβ 1-42 (r = -0.3025, p = 0.0002), and positively correlated with Aβ 1-42/Aβ 1-40 ratio (r = 0.2176, p = 0.0086). Conclusions: These findings suggest that cognitive impairment in older adults is strongly associated with amyloid burden, oxidative stress, and age, whereas vitamin D status was not directly correlated with cognitive performance in this cohort.