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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. 2b
Reference
Study design: Randomized controlled trial (double-blinded)
Funding: Government
Setting: Population-based
Synopsis
These authors recruited African-American women from various community settings. During a pre-enrollment telephone interview, women were asked not to take vitamin D–containing supplements for 4 to 6 weeks before the study. The researchers then measured their serum vitamin D levels and included those women with levels between 8 ng/mL and 26 ng/mL. 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 the women to receive daily vitamin D3 (2400 IU, 3600 IU, or 4800 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 3 months to achieve a target level of 30 ng/mL. They also gave women in each group 1200 mg calcium daily. The researchers assessed the MMSE score every 6 months for 3 years and used a score of less than 27 as the cutoff for mild cognitive impairment. Unfortunately, 74 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, unfortunately, don't provide sample size or power estimates for the study. Finally, they properly recognize the limitations of the MMSE in detecting cognitive decline.
Reviewer
Henry C. Barry, MD, MS
Professor
Michigan State University
East Lansing, MI
Comments
The study shows that Vit D…
The study shows that Vit D supplemention has no significant advantage in improving cognition in women with low vit D compared with placebo
Poor study
Study lacks research rigour. Misleading summary presented except for the last few sentences. Another study limitation: direct calcium supplementation, as opposed to ensuring proper dietary levels of Calcium, is now discouraged by major Endocrine associations as it is associated with greater risk of vascular diseases and so, presumably, also possible vascular effects on dementia risks.