Archief Roodbont

January 17, 2008 (Auckland, New Zealand) – A new study has shown that calcium supplementation might increase vascular events in elderly women [1]. The findings are somewhat unexpected, because previous trials have shown that calcium improves blood cholesterol levels, senior author Dr Ian R Reid (University of Auckland, New Zealand) told heartwire.

Dr Mark J Bolland (University of Auckland, New Zealand) and colleagues published the findings online in BMJ January 15, 2008.

"This is quite controversial, given that the worldwide calcium-supplement market is worth $3 billion a year," says Reid. "The trial was primarily looking at what calcium supplements do to bone density, but we had a secondary hypothesis right from the outset that calcium might actually prevent heart attack. What we found, to our surprise, was that we didn't see a decrease but an increase, and the findings appear to be quite robust." Reid added, however, that there have been some clues from three other recent studies, including one from Women's Health Initiative (WHI) in the US [2]: "these three did not find significant increases in the number of heart attacks [with calcium], but they have found upward trends."

Dr Erin D Michos (Johns Hopkins University, Baltimore, MD), who was not involved with this new study but cowrote an editorial accompanying the publication of the WHI study on vitamin-D/calcium supplements last year [3], told heartwire: "This is a thought-provoking study, although not definitive, but further work should be done."

Others warned that it is premature to make any treatment decisions on the basis of this new study. British Heart Foundation spokesperson Judy O'Sullivan said more rigorous research was needed before any firm conclusions could be drawn. "Anyone who has been advised by their doctor to take calcium supplements to protect their bones should not stop doing so in light of this study alone without medical advice," she said.

Findings equivocal

The New Zealand team randomized 1471 postmenopausal women (average age 74 years) to either calcium supplementation (1 g/day calcium citrate) or placebo. As well as bone density, they looked at adverse cardiovascular events over five years: death, sudden death, MI, angina, other chest pain, stroke, transient ischemic attack, and a composite end point of MI, stroke, or sudden death.

Reid says the study collected data on MIs and strokes "in a much more careful way" than any other previous studies have done. "We got cardiologists and other people involved and audited all those things and went back to patients' hospital records and so on."

MI was more commonly reported in the calcium group than in the placebo group (45 events in 31 women vs 19 events in 14 women, p=0.01), and the composite end point was also reached more often in the calcium group (101 events in 69 women vs 54 events in 42 women, p=0.008). Even after adjudication, MI remained more common in the calcium group, as did the composite end point.

# posted by roodbont @ 1:09 AM