# Association of serum 25(OH)D3 and cognitive levels with biological aging in the elderly: a cross-sectional study

## TL;DR

This study finds that low vitamin D levels and poor cognitive performance in older adults are linked to faster biological aging.

## Contribution

The study is the first to examine the combined effect of vitamin D deficiency and cognitive impairment on biological aging.

## Key findings

- Low cognitive performance is associated with increased biological aging risk.
- Low vitamin D levels show a U-shaped relationship with biological aging.
- Combined low vitamin D and low cognition result in the highest biological aging risk.

## Abstract

Biological aging, a fundamental process affecting health and longevity, is pivotal to understanding the physiological decline associated with aging. Serum vitamin D3 deficiency and cognitive impairment are common health issues among older adults. However, the joint associations of serum vitamin D levels and cognitive impairment with biological aging remain poorly understood. This study aims to evaluate the independent and combined associations of serum vitamin D3 and cognitive impairment with biological aging in older adults.

This cross-sectional study included adults aged 60 years and older from the 2011–2014 National Health and Nutrition Examination Survey (NHANES). Biological aging was measured using Phenotypic Age calculated from biomarkers. Cognitive performance was assessed using the Centre for the Establishment of a Registry for Alzheimer’s Disease (CERAD) test, the Animal Fluency test (AFT), and the Digit Symbol Substitution test (DSST). Multivariable regression and restricted cubic spline models were used to examine the relationships between serum 25(OH)D3 levels, cognitive performance, and biological aging.

After adjusting for all covariates, individuals in the highest quartile of cognitive performance had a reduced risk of biological aging compared to those in the lowest quartile (CERAD: OR 0.91; 95% CI, 0.57–1.46; AFT: OR 0.48; 95% CI, 0.29–0.82; DSST: OR 0.43; 95% CI, 0.24–0.77). A U-shaped relationship was observed between serum 25(OH)D3 levels and biological aging. Combined analyses revealed that individuals with both low serum 25(OH)D3 and low cognitive performance had the highest risk of biological aging across all cognitive tests (CERAD: OR 1.43; 95% CI, 1.02–1.98; AFT: OR 1.70; 95% CI, 1.24–2.32; DSST: OR 1.67; 95% CI, 1.22–2.27). Notably, in the DSST, individuals with normal serum 25(OH)D3 levels and normal cognitive performance showed a reduction in Phenotypic Age by 2.40 years (p < 0.01).

In older adults, low serum 25(OH)D3 levels combined with low cognitive performance are strongly associated with an increased risk of biological aging.