Calcium and Vitamin D Supplementation and Cognitive Impairment in the Women's Health Initiative

Objectives To examine the effects of vitamin D and calcium on cognitive outcomes in elderly women. Design Post hoc analysis of a randomized double‐blind placebo‐controlled trial. Setting Forty Women's Health Initiative (WHI) clinical centers across the United States. Participants Four thousand one hundred forty‐three women aged 65 and older without probable dementia at baseline who participated in the WHI Calcium and Vitamin D Trial and the WHI Memory Study. Intervention Two thousand thirty‐four women were randomized to receive 1,000 mg of calcium carbonate combined with 400 IU of vitamin D3 (treatment) and 2,109 to placebo. Measurements Primary: classifications of probable dementia or mild cognitive impairment (MCI) based on a four‐phase protocol that included central adjudication. Secondary: global cognitive function and individual cognitive subtests. Results Mean age of participants was 71. During a mean follow‐up of 7.8 years, 39 participants in the treatment group and 37 in the placebo group developed incident dementia (hazard ratio (HR) = 1.11, 95% confidence interval (CI) = 0.71–1.74, P = .64). Likewise, 98 treatment participants and 108 placebo participants developed incident MCI (HR = 0.95, 95% CI = 0.72–1.25, P = .72). There were no significant differences in incident dementia or MCI or in global or domain‐specific cognitive function between groups. Conclusion There was no association between treatment assignment and incident cognitive impairment. Further studies are needed to investigate the effects of vitamin D and calcium separately, on men, in other age and ethnic groups, and with other doses.