Calcium supplements implicated in increased risk for CV events
Bolland M. BMJ. 2011;doi:10.1136/bmj.d2040.
Calcium supplements, taken with or without vitamin D, have been shown to modestly increase the risk for CV events, including MI and stroke.
These results, reported in a new study published by the British Medical Journal, incorporated findings from a re-analysis of the Women’s Health Initiative Calcium/Vitamin D Supplementation Study (WHI CaD), as well as a meta-analysis of several additional trials.
Initially, results from WHI CaD, which was a 7-year, randomized, placebo-controlled trial with 36,282 postmenopausal women, showed no adverse effect of calcium and vitamin D on any CV endpoint. The results were obscured, however, because participants had free access to those supplements, according to the researchers. Specifically, at randomization, 54% of the participants were taking personal calcium supplements and 47% personal vitamin D supplements, which researchers said rendered the trial a comparison of higher- and lower-dose calcium and vitamin D for most of those participating.
According to results of their re-analysis, the 46% (n=16,718) of women not taking personal calcium supplements had an HR of 1.13 for any CV endpoint and 1.20 for total MI (P=.07 for both). Results on the other endpoints, including revascularization and stroke, were similar, with the exception of all-cause mortality (HR=0.99). Designation to calcium and vitamin D among women taking personal calcium supplements did not change CV risk.
“By restricting the analyses to women not taking personal calcium supplements, we were able to estimate the effect of calcium and vitamin D on CV events, observing increased risks of these events with calcium and vitamin D,” the researchers wrote.
To gain further insight into this issue, investigators then supplemented these results with data from placebo-controlled trials that examined CV events among individuals taking calcium or calcium and vitamin D. The complete trial-level data were obtained from 28,072 individuals from eight trials, as well as the WHI CaD participants who did not take personal calcium supplements.
Overall, 1,835 died during the mean trial duration of 5.7 years, which was weighted by study size. Researchers reported that 1,384 individuals had an incident MI or stroke, which resulted in RRs of 1.24 (P=.004) for MI and 1.15 (P=.009) for the composite of MI and stroke.
“When [WHI CaD] results are taken together with the results of other clinical trials of calcium supplements, with or without vitamin D, they strongly suggest that calcium supplements modestly increase the risk of CV events, particularly MI,” the researchers concluded. “These data justify a reassessment of the use of calcium supplements in older people.”
The situation seems quite complex to me because there are different reasons to supplement with calcium. For example, there are people who have conditions like osteoporosis, renal disease, and who are receiving treatment under clinical supervision. There are people at varying levels of osteoporosis risk, some of whom take calcium with or without vitamin D on their own prophylactically, and some who take it under clinical supervision based on recommendations from their physicians. There are people who take calcium and other supplements for general health reasons with the belief that anything natural must be good. Some people take calcium as part of antacid preparations — it is not clear to me how this is captured in the studies included in this meta-analysis. It is also unclear to me how antacid use was cross-referenced with calcium use in WHI.
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ICD nonuse in eligible patients may be lower than previously estimated
LaPointe N. Circ Cardiovasc Qual Outcomes. 2011;4:146-151.
Detailed analysis showed that rates of underutilization of implantable cardioverter defibrillators among eligible patients decreased from 41% to 13%, according to newly published data.
“To date, several analyses of claims or registry data have indicated high rates of underutilization of this evidence-based therapy in clinical practice, as well as age, sex and racial disparities in ICD use,” the researchers wrote. “Although we initially identified similar rates of ICD underutilization and disparities within our health care system, after detailed medical record abstraction, we discovered that a majority of those not receiving an ICD had an identified contraindication or patient refusal.”
Their analysis included patients (n=542) with a diagnosis of HF and left ventricular ejection fraction of no more than 30% at a tertiary care center from Jan. 1, 2007, to Aug. 30, 2007. With the use of medical records, researchers determined reasons for nonuse among patients without an ICD.
Overall, 224 eligible patients (41%) did not receive an ICD. Adjusted analysis comparing all ICD recipients with all nonrecipients revealed absence of ventricular arrhythmia or cardiac arrest (OR=3.17; 95% CI, 2.14-4.68), index hospitalization on a noncardiology service (OR=2.64; 95% CI, 1.65-4.21) and female sex (OR=1.90; 95% CI, 1.28-2.81) as being the factors most associated with nonuse.
After performing a detailed chart review on the eligible patients, researchers observed that 117 patients (52%) were ineligible for the device and 38 (17%) refused it, leading to only 69 (13%) patients eligible for an ICD who failed to receive one.
Furthermore, analysis comparing all ICD recipients with nonrecipients without contraindications indicated the following characteristics of nonuse: absence of ventricular arrhythmias (OR=4.93; 95% CI, 2.56-9.5), noncardiology hospital service (OR=3.73; 95% CI, 1.98-7.04) and no health insurance (OR=3.10; 95% CI, 1.48-6.46).