The Journals of Gerontology Series A: Biological Sciences and Medical Sciences Advance Access published online on February 16, 2009
The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, doi:10.1093/gerona/glp006
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Calcium Plus Vitamin D Supplementation and Mortality in Postmenopausal Women: The Women's Health Initiative Calcium–Vitamin D Randomized Controlled Trial
1 Division of Public Health Sciences, WHI Clinical Coordinating Center, Fred Hutchinson Cancer Research Center, Seattle, Washington
2 Division of Epidemiology, Department of Population Health, Health Policy Institute, Medical College of Wisconsin, Milwaukee
3 Department of Obstetrics and Gynecology, Division of Reproductive Endocrinology and Infertility, University of Texas, Health Science Center, San Antonio
4 Department of Epidemiology, University of Pittsburgh, Pennsylvania
5 Department of Medicine, Epidemiology and Biostatistics, University of California at San Francisco
6 Department of Medicine, University of Cincinnati, Ohio
7 Department of Medicine, Health Science Center, University of Tennessee, Memphis
8 Department of Internal Medicine, Women's Health, Mayo Clinic Scottsdale, Arizona
9 Department of Epidemiology, Division of Preventive Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
10 Stanford Prevention Research Center, School of Medicine, Stanford University, California
11 Department of Social and Preventive Medicine, University at Buffalo, New York
Address correspondence to Andrea Z. LaCroix, PhD, WHI Clinical Coordinating Center, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, M3-A410, P.O. Box 19024, Seattle, WA 98109-1024. Email: alacroix{at}whi.org
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Abstract |
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Background: Calcium and vitamin D (CaD) supplementation trials including the Women's Health Initiative (WHI) trial of CaD have shown nonsignificant reductions in total mortality. This report examines intervention effects on total and cause-specific mortality by age and adherence.
Methods: The WHI CaD trial was a randomized, double-blind, placebo-controlled trial that enrolled 36,282 postmenopausal women aged 51–82 years from 40 U.S. clinical centers. Women were assigned to 1,000 mg of elemental calcium carbonate and 400 IU of vitamin D3 daily or placebo with average follow-up of 7.0 years.
Results: The hazard ratio (HR) for total mortality was 0.91 (95% confidence interval [CI], 0.83–1.01) with 744 deaths in women randomized to CaD versus 807 deaths in the placebo group. HRs were in the direction of reduced risk but nonsignificant for stroke and cancer mortality, but near unity for coronary heart disease and other causes of death. HRs for total mortality were 0.89 in the 29,942 women younger than 70 years (95% CI, 0.79–1.01) and 0.95 in the 6,340 women aged 70 and older (95% CI, 0.80–1.12; p value for age interaction = .10). No statistically significant interactions were observed for any baseline characteristics. Treatment effects did not vary significantly by season.
Conclusions: In the WHI CaD trial, supplementation did not have a statistically significant effect on mortality rates but the findings support the possibility that these supplements may reduce mortality rates in postmenopausal women. These data can neither support nor refute recommendations for higher dose vitamin D supplementation to reduce cancer or total mortality.
Keywords Calcium; Vitamin D; Mortality; Cause-specific mortality; Women's Health Initiative
Received: July 6, 2008; Accepted: December 23, 2008