Low Vitamin D and Brain Health in Older Adults

by | May 3, 2016 | 2014, Brain Health, Cognitive Health, Vitamin D - Mental Health

Written by Marcia J. Egles, MD. Study examines a possible relationship between serum vitamin D levels and cognitive decline.

A recent study reports a link between low vitamin D levels and decline in brain function over time in older adults (1). Despite research showing the presence of a vitamin D receptor in the brain cells of both humans and animals, clear relationships between vitamin D levels and cognition have yet to be established (1,7).

Older adults may be at an especially high risk for vitamin D deficiency due to their skin’s decreased ability make vitamin D and due to low dietary intake of vitamin D. The capacity of the skin’s ability to synthesize vitamin D is reduced by more than 50% at 70 years of age compared to 20 years of age (2). Although aging itself does not affect the intestinal absorption of dietary vitamin D, many elderly have poor intakes of vitamin D from such causes as malnutrition and poor health (2, 5, 7).

The researchers looked at 2,777 well-functioning adults aged 70 to 79 whose cognitive function was measured at the study’s onset and again four years later. The subjects were community-dwellers from Pittsburgh, PA or Memphis, TN. Females comprised 48.8% of the group. Vitamin D levels, that is, serum 25-hydroxyvitamin D levels, were measured at baseline and at a 12 month follow-up. Cognitive function was measured at baseline and at a 4 year follow-up. Cognition was measured using the 100-point “Modified Mini Mental State Examination” (3) and the Digit Symbol Substitution Test (4), both well-established tests. The first test assesses a person’s orientation, concentration, recall, language, verbal fluency, and visual spatial reasoning. The second measure, the Digit Symbol Substitution Test, is a 90 second timed test that assesses processing speed, executive function, and working memory.

Vitamin D status was categorized into three groups: 25(OH)D levels of less than 20.0 nanograms per milliliter, 20.0 to 29.9 ng/ml, or 30.0ng/ml or greater. Those with the lowest Vitamin D levels comprised 32.9% of the study population. Those in the insufficient range with 25(OH) D more than 20.0 and less than 30 ng/ml were 35.5% of the population. While a precise definition of vitamin D deficiency has been controversial, currently the US Endocrine Society regards levels of 25(OH)D under 20 ng/ml as deficient (5). The population studied in this publication would qualify as largely deficient or insufficient in Vitamin D. (Based on the definition of the US Endocrine Society, the prevalence of vitamin D deficiency in general is almost one-third of the US population (6)).

The lower 25(OH)D levels were associated with lowest baseline cognitive scores on the Modified Mini Mental Status Examination. The data analysis included statistical adjustments for variables such as age, education, sex, race, site, season, physical activity and illnesses.

Those with the lowest Vitamin D status (less than 20 ng/ml) had a mean adjusted score of 89.9 on the 100 point scale. (95% confidence interval = 89.4-90.4). Those in the 20.0-29.9 ng range of 25 (OH) D per milliliter serum had baseline mean scores of 90.8 (CI= 90.4-91.3). Those 30ng and above had a mean baseline score 90.6, 95%CI=90.2-91.1, p trend=0.2. Participants with low 25(OH)D levels had greater declines in the Modified Mini Mental Status Exam over 4 years than those with higher levels. (Least square mean change -1.0, -0.8 and -0.2 respectively for the three groups, p=0.05.) There was no significant decline in the Digital Symbol Substitution Test scores according to 25(OH)D level.

As observed by the study’s authors, Vitamin D deficiency and cognitive impairment are both common in older adults. However, this study does not establish that Vitamin D deficiency causes cognitive impairment, nor does it show that correction of vitamin D inadequacies would prevent dementia. Long term clinical trials are needed to determine whether vitamin D supplementation can prevent cognitive impairments (7).

Source: Wilson, Valerie K., et al. “Relationship Between 25‐Hydroxyvitamin D and Cognitive Function in Older Adults: The Health, Aging and Body Composition Study.” Journal of the American Geriatrics Society 62.4 (2014): 636-641.

© 2014, Copyright the Authors, Journal compilation © 2014, The American Geriatrics Society

Posted July 7, 2014.

References:

  1. Wilson, Valerie K. and Denise K. Houston, PhD, Laurel Kilpatrick, MD, James Lovato, MS et al. Relationship Between 25-Hydroxyvitamin D and CognitiveFunction in Older Adults: The Health, Aging and Body Composition Study. JAGS 62:636-641, 2014.
  2. MacLaughlin J, Holick MF. Aging decreases the capacity of human skin to produce vitamin D3. J Clin Invest. 1985;76(4):1536–1538. [PMC free article] [PubMed]
  3. Teng EL, Chui HC. The Modified Mini-Mental State (3MS) examination.J Clin Psychiatry 1987;48:314–318.
  4. Wechsler D. WAIS-R: Manual: Wechsler Adult Intelligence Scale—Revised.New York: Harcourt Brace Jovanovich for Psychological Corp, 1981.
  5. Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Endocrine Society Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96(7):1911–1930. [PubMed]
  6. Ganji V, Zhang X, Tangpricha V. Serum 25-hydroxyvitamin D concentrations and prevalence estimates of hypovitaminosis D in the US population based on assay-adjusted data. J Nutr. 2012;142(3):498–507. [PubMed]]
  7. Schlogl, Mathias and Michael F. Holick .  Vitamin D and neurocognitive function, Clin Interv Aging. 2014; 9: 559–568. Published online Apr 2, 2014.