UCSF

Objectives

To examine the relationship between 25-hydroxyvitamin D (25(OH)D) levels and cognitive performance over time in older adults in the Health, Aging and Body Composition (Health ABC) Study.

Design

Prospective cohort study.

Setting

Community-dwelling participants in Pittsburgh, Pennsylvania, and Memphis, Tennessee.

Participants

Well-functioning adults aged 70 to 79 at baseline with serum 25(OH)D measured at the 12-month follow-up visit and cognitive function measured at baseline and 4-year follow-up visit (N = 2,777).

Measurements

Vitamin D status was categorized as 25(OH)D levels of less than 20.0 ng/mL, 20.0 to 29.9 ng/mL, or 30.0 ng/mL or greater. Cognition was measured using the modified Mini-Mental State Examination (3MS) and Digit Symbol Substitution Test (DSST). Linear regression models adjusting for multiple covariates, including age, education, sex, race, site, season, physical activity, and comorbidities, were used in the analysis.

Results

Sixty-eight percent of participants had 25(OH)D levels of less than 30.0 ng/mL. Lower 25(OH)D levels were associated with lower baseline cognitive scores on the 3MS (adjusted mean 89.9, 95% confidence interval (CI) = 89.4-90.4 for <20.0 ng/mL; adjusted mean 90.8, 95% CI = 90.4-91.3 for 20.0-29.9 ng/mL; adjusted mean 90.6, 95% CI = 90.2-91.1 for ≥ 30.0 ng/mL; P trend = .02) and the DSST (adjusted mean 35.2, 95% CI = 34.5-36.0 for <20.0 ng/mL; adjusted mean 35.9, 95% CI = 35.2-36.6 for 20.0-29.9 ng/mL; adjusted mean 37.0, 95% CI = 36.3-37.8 for ≥ 30.0 ng/mL; P trend = .01). Participants with low 25(OH)D levels had greater declines in 3MS scores over 4 years than those with higher levels (least square mean change -1.0, 95% CI = -1.5 to -0.6 for <20.0 ng/mL; least square mean change -0.8, 95% CI = -1.2 to -0.3 for 20.0-29.9 ng/mL; least square mean change -0.2, 95% CI = -0.7 to 0.2 for ≥30.0 ng/mL; P = .05). There was no significant difference in DSST decline according to 25(OH)D level.

Conclusion

Low 25(OH)D levels were associated with worse global cognitive function and greater decline over time according to the 3MS. Intervention trials are needed to determine whether vitamin D supplementation can reduce cognitive decline.