The use of calcium supplements, common among the elderly today, was linked with an elevated risk for cardiovascular death in men, a new study found.
Compared with men who did not take calcium supplements, those taking more than 1,000 mg per day had a 20 percent higher risk of dying from cardiovascular disease, Qian Xiao of the National Cancer Institute in Bethesda, Md., and colleagues reported in JAMA Internal Medicine.
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Early studies suggested that calcium supplementation might provide cardiovascular benefits through blood pressure or lipid effects, but more recent analyses have suggested that the supplements might actually be harmful to cardiovascular health.
To clarify these discrepancies, Xiao and colleagues analyzed data from the National Institutes of Health-AARP Diet and Health Study, which enrolled almost 600,000 adults ages 50 to 71 in 1995 and 1996.
At baseline, participants completed a questionnaire detailing their eating habits, medical history, and lifestyle.
Among the 388,229 participants included in the analysis, 56 percent of women and 23 percent of men reported using calcium supplements, while 58 percent and 56 percent reported taking multivitamins that contained calcium.
Those in the highest quintile of calcium supplement use were more often white, college-educated, and physically active, and were less likely to be smokers or to have a high intake of red meat and dietary fat.
During 12 years of follow-up, 7,904 men and 3,874 women died of cardiovascular disease.
Along with the increased risk for all cardiovascular disease deaths and heart disease deaths in men, calcium supplementation also was associated with an elevated risk for death from cerebrovascular disease, but the relative risk did not reach statistical significance.
This may have resulted from there being only 36 cases of fatal cerebrovascular events, according to the researchers.
In contrast to men, no increased risks with supplementation were seen for women.
For total calcium intake -- dietary plus supplementation -- men in the highest quintile of intake again were at increased risk for all cardiovascular disease mortality and death from heart disease.
They also had a nonsignificant increase for cerebrovascular death.
Total calcium intake was not linked with increased cardiovascular mortality in women.
The researchers also analyzed the data for individuals taking calcium-only supplements, to rule out possible effects from other micronutrients contained in multivitamin supplements, and found that once again there was an increase in the risk of death from cardiovascular disease in the study population.
They then looked for interactions between calcium supplement use and a number of other factors such as age, smoking, body mass index, and dyslipidemia, and found a significant interaction for men with smoking.
In women, they noted an interaction for calcium use and past smoking and high cholesterol.
The researchers noted that the different risks for men and women were "intriguing," in light of the fact that a reanalysis of data from the Women's Health Initiative identified "modest" increases in risk for cardiovascular events, particularly myocardial infarction, in supplement users.