Affiliations: [a] Division of Epidemiology, Department of Family Medicine and Public Health, University of California San Diego, La Jolla, CA, USA
| [b] Department of Radiology, University of California San Diego, La Jolla, CA, USA
| [c] Division of General Internal Medicine, Department of Medicine, VA San Diego Healthcare System, University of California San Diego, San Diego, CA, USA
Correspondence:
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Correspondence to: Gail A. Laughlin, PhD, Department of Family Medicine and Public Health, University of California San Diego, 9500 Gilman Drive, MC0725, La Jolla, CA 92093, USA. Tel.: +1 858 822 2416; Fax: +1 858 534 4642; E-mail: glaughlin@ucsd.edu.
Abstract: Background: Evidence of a role for vitamin D (VitD) in cognitive aging is mixed and based primarily on extreme VitD deficiency. We evaluated the association of VitD insufficiency with cognitive function in older, community-dwelling adults living in a temperate climate with year-round sunshine. Methods: A population-based longitudinal study of 1,058 adults (median age 75; 62% women) who had cognitive function assessed and serum levels of 25-hydroxyvitaminD (25OHD) measured in 1997–99 and were followed for up to three additional cognitive function assessments over a 12-year period. Results: Overall, 14% (n = 145) of participants had VitD insufficiency defined as 25OHD <30 ng/ml. Adjusting for age, sex, education, and season, VitD insufficiency was associated with poorer baseline performance on the Mini-Mental Status Exam (MMSE) (p = 0.013), Trails Making Test B (Trails B) (p = 0.015), Category Fluency (p = 0.006), and Long Term Retrieval (p = 0.019); differences were equivalent to 5 years of age. For those with VitD insufficiency, the odds of mildly impaired performance at baseline were 38% higher for MMSE (p = 0.08), 78% higher for Trails B (p = 0.017), and 2-fold higher for Category Fluency and Long Term Retrieval (both p = 0.001). VitD insufficiency was not related to the rate of cognitive decline on any test or the risk of developing impaired performance during follow-up. Conclusion: In this population with little VitD deficiency, even moderately low VitD was associated with poorer performance on multiple domains of cognitive function. Low VitD did not predict 12-year cognitive decline. Clinical trials are essential to establish a causal link between VitD and cognitive well-being.
Keywords: Cognitive aging, cognitive function, epidemiology, longitudinal study, vitamin D
