Dietary supplements and mortality rate in older women: the Iowa Women's Health Study.
Study Goal
The researchers aimed to determine the association between calcium supplementation and total mortality risk in older women.
Results Summary
Calcium use was inversely related to total mortality, showing a hazard ratio of 0.91 (95% CI: 0.88-0.94) and an absolute risk reduction of 3.8%. This finding was replicated in shorter-term analyses, suggesting a consistent protective effect.
Population
38,772 older women (mean age 61.6 years at baseline) from the Iowa Women's Health Study.
Effective Dosage
Not specified
Duration
Follow-up from 1986 to 2008 (22 years) with additional shorter-term analyses (10-year, 6-year, and 4-year follow-ups).
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
multivitamins | increase | total mortality | 38,772 older women in the Iowa Women's Health Study | hazard ratio, 1.06; 95% CI, 1.02-1.10; absolute risk increase, 2.4% | associated with increased risk | #1 |
vitamin B(6) | increase | total mortality | 38,772 older women in the Iowa Women's Health Study | 1.10; 1.01-1.21; 4.1% | associated with increased risk | #2 |
folic acid | increase | total mortality | 38,772 older women in the Iowa Women's Health Study | 1.15; 1.00-1.32; 5.9% | associated with increased risk | #3 |
iron | increase | total mortality | 38,772 older women in the Iowa Women's Health Study | 1.10; 1.03-1.17; 3.9% | associated with increased risk | #4 |
magnesium | increase | total mortality | 38,772 older women in the Iowa Women's Health Study | 1.08; 1.01-1.15; 3.6% | associated with increased risk | #5 |
zinc | increase | total mortality | 38,772 older women in the Iowa Women's Health Study | 1.08; 1.01-1.15; 3.0% | associated with increased risk | #6 |
copper | increase | total mortality | 38,772 older women in the Iowa Women's Health Study | 1.45; 1.20-1.75; 18.0% | associated with increased risk | #7 |
calcium | decrease | total mortality | 38,772 older women in the Iowa Women's Health Study | hazard ratio, 0.91; 95% confidence interval, 0.88-0.94; absolute risk reduction, 3.8% | inversely related | #8 |
iron | increase | total mortality | separate, shorter-term analyses (10-year, 6-year, and 4-year follow-up), each with approximately 15% of the original participants having died | - | findings were replicated | #9 |
calcium | decrease | total mortality | separate, shorter-term analyses (10-year, 6-year, and 4-year follow-up), each with approximately 15% of the original participants having died | - | findings were replicated | #10 |
BACKGROUND: Although dietary supplements are commonly taken to prevent chronic disease, the long-term health consequences of many compounds are unknown. METHODS: We assessed the use of vitamin and mineral supplements in relation to total mortality in 38,772 older women in the Iowa Women's Health Study; mean age was 61.6 years at baseline in 1986. Supplement use was self-reported in 1986, 1997, and 2004. Through December 31, 2008, a total of 15,594 deaths (40.2%) were identified through the State Health Registry of Iowa and the National Death Index. RESULTS: In multivariable adjusted proportional hazards regression models, the use of multivitamins (hazard ratio, 1.06; 95% CI, 1.02-1.10; absolute risk increase, 2.4%), vitamin B(6) (1.10; 1.01-1.21; 4.1%), folic acid (1.15; 1.00-1.32; 5.9%), iron (1.10; 1.03-1.17; 3.9%), magnesium (1.08; 1.01-1.15; 3.6%), zinc (1.08; 1.01-1.15; 3.0%), and copper (1.45; 1.20-1.75; 18.0%) were associated with increased risk of total mortality when compared with corresponding nonuse. Use of calcium was inversely related (hazard ratio, 0.91; 95% confidence interval, 0.88-0.94; absolute risk reduction, 3.8%). Findings for iron and calcium were replicated in separate, shorter-term analyses (10-year, 6-year, and 4-year follow-up), each with approximately 15% of the original participants having died, starting in 1986, 1997, and 2004. CONCLUSIONS: In older women, several commonly used dietary vitamin and mineral supplements may be associated with increased total mortality risk; this association is strongest with supplemental iron. In contrast to the findings of many studies, calcium is associated with decreased risk.