The presentation of this paper and its results are flawed.
The title and abstract of this paper fail to disclose that this
article is merely a rehash of data used in an older randomised trial with
a different primary endpoint. As many readers will only read the abstract,
this is misleading.
Tables 2 and 3 describe the incidence of vascular events as reported
by the patients themselves. The inaccuracy of this method of collating
data is demonstrated by the authors themselves in table 4 which shows the
actual events as documented in hospital records. Surely this is a more
accurate method of data collection, therefore tables 2 and 3, which are
inaccurate, should not have been reported or described in the abstract.
There are no statistically significant findings in table 4 which
looks at the rates of vascular events as obtained from hospital records.
Therefore this is a negative study and the discussion should clarify this.
The only positive finding is that patients who take calcium are more
likely to 'report' that they have had a myocardial infarction.
Instead, the discussion is heavily biased towards cautioning the
prescribing of calcium supplements, as if there were a meaningful positive
finding in this study.
The findings of this study were presented at an American Society of
Bone and Mineral Research conference before publication. The New Zealand
Listener, a weekly magazine, ran an article in an October 2007 issue
describing the results...
"There were fewer broken bones and a 75 percent reduction in loss of
bone density in the group taking supplements, but further analysis of the
research data showed a worrying trend. There were 36 heart attacks among
the group taking calcium supplements, and 22 among those taking a placebo.
The chances of having a heart attack or a stroke increased by up to 50
percent in the group taking supplements.
Professor Ian Reid, a professor of medicine at Auckland University,
says the results were unexpected and very significant. “The message seems
to be that very high doses of calcium supplements can help bone density,
but this may come at too high a cost.” " 1.
Clever use of relative risk to accentuate the findings but the
results described by this magazine do not agree with those in this
article. Professor Reid suggests that the risk of calcium supplements may
outweight the benefits, but this is not at all clear in this published
article.
Finally, in the original trial publication, there was a high dropout
rate and the abstract concludes that ..."Poor long-term compliance limits
its effectiveness." 2.
If drop-out rates and poor compliance were significant, these should also
have been documented in this article.
Overall, this is a poor example of searching for publishable material
in old data. The results have been misrepresented and the NZ lay public
have been informed before publication, which makes it difficult for NZ
general practitioners to advise their patients should their calcium
supplementation be questioned.
2. Reid et al. Randomized Controlled Trial of Calcium in Healthy
Older Women. The American Journal of Medicine
Volume 119, Issue 9, September 2006, Pages 777-785
Rapid Response:
Bad science
Dear Editor,
The presentation of this paper and its results are flawed.
The title and abstract of this paper fail to disclose that this
article is merely a rehash of data used in an older randomised trial with
a different primary endpoint. As many readers will only read the abstract,
this is misleading.
Tables 2 and 3 describe the incidence of vascular events as reported
by the patients themselves. The inaccuracy of this method of collating
data is demonstrated by the authors themselves in table 4 which shows the
actual events as documented in hospital records. Surely this is a more
accurate method of data collection, therefore tables 2 and 3, which are
inaccurate, should not have been reported or described in the abstract.
There are no statistically significant findings in table 4 which
looks at the rates of vascular events as obtained from hospital records.
Therefore this is a negative study and the discussion should clarify this.
The only positive finding is that patients who take calcium are more
likely to 'report' that they have had a myocardial infarction.
Instead, the discussion is heavily biased towards cautioning the
prescribing of calcium supplements, as if there were a meaningful positive
finding in this study.
The findings of this study were presented at an American Society of
Bone and Mineral Research conference before publication. The New Zealand
Listener, a weekly magazine, ran an article in an October 2007 issue
describing the results...
"There were fewer broken bones and a 75 percent reduction in loss of
bone density in the group taking supplements, but further analysis of the
research data showed a worrying trend. There were 36 heart attacks among
the group taking calcium supplements, and 22 among those taking a placebo.
The chances of having a heart attack or a stroke increased by up to 50
percent in the group taking supplements.
Professor Ian Reid, a professor of medicine at Auckland University,
says the results were unexpected and very significant. “The message seems
to be that very high doses of calcium supplements can help bone density,
but this may come at too high a cost.” " 1.
Clever use of relative risk to accentuate the findings but the
results described by this magazine do not agree with those in this
article. Professor Reid suggests that the risk of calcium supplements may
outweight the benefits, but this is not at all clear in this published
article.
Finally, in the original trial publication, there was a high dropout
rate and the abstract concludes that ..."Poor long-term compliance limits
its effectiveness." 2.
If drop-out rates and poor compliance were significant, these should also
have been documented in this article.
Overall, this is a poor example of searching for publishable material
in old data. The results have been misrepresented and the NZ lay public
have been informed before publication, which makes it difficult for NZ
general practitioners to advise their patients should their calcium
supplementation be questioned.
1. "Crunch Time", Linley Boniface, NZ Listener. October 13-19 2007
Vol 210 No 3518
http://www.listener.co.nz/issue/3518/columnists/9789/crunch_time.html
2. Reid et al. Randomized Controlled Trial of Calcium in Healthy
Older Women. The American Journal of Medicine
Volume 119, Issue 9, September 2006, Pages 777-785
Competing interests:
None declared
Competing interests: No competing interests