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Am Fam Physician. 2019;100(2):118

Clinical Question

Is vitamin D more effective than placebo in preventing cognitive decline in African American women older than 65 years who have low serum vitamin D levels at baseline?

Bottom Line

No. (Level of Evidence = 2b)


The authors recruited African American women from various community settings. During a preenrollment telephone interview, women were asked not to take vitamin D– containing supplements for four to six weeks before the study. The researchers then measured their plasma vitamin D levels and included those women with levels between 8 ng per mL (20 nmol per L) and 26 ng per mL (65 nmol per L). They excluded women with hip osteoporosis, Mini-Mental State Examination (MMSE) scores of less than 21, moderate to severe vertebral fractures, liver disease, or kidney stones. The researchers randomly assigned half of the women to receive daily vitamin D3 (i.e., 2,400 IU, 3,600 IU, or 4,800 IU; n = 130) and the other half to receive matching placebo (n = 130). They used the baseline vitamin D level to determine the initial dose, then titrated the dose every three months to achieve a target level of 30 ng per mL (75 nmol per L). They also gave women in each group 1,200 mg of calcium daily. The researchers assessed the MMSE score every six months for three years and used a score of less than 27 as the cutoff for mild cognitive impairment. Seventy-four women dropped out of the study, which raises serious concerns about trusting the final results. Among the women who completed the study, the MMSE scores increased in both groups, and the degree of improvement was comparable. The authors report no vitamin D–related adverse events. The authors do not provide sample size or power estimates for the study. They properly recognize the limitations of the MMSE in detecting cognitive decline.

Study design: Randomized controlled trial (double-blinded)

Funding source: Government

Allocation: Concealed

Setting: Population-based

Reference: OwusuJEIslamSKatumuluwaSSet alCognition and vitamin D in older African-American women–physical performance and osteoporosis prevention with vitamin D in older African Americans trial and dementia. J Am Geriatr Soc2019;67(1):81–86.

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