This trial treatment with niacin
offers disturbing results in the fight to prevent strokes and heart attacks.
By Dr. Theodore Dalrymple in PJ Media
What stands to reason is not always borne out by facts, for
reality is often refractory to human wishes. There was a good illustration of
this unfortunate principle in a recent edition of the New England Journal of
Medicine.
It has long been known that low concentrations of high-density
lipoproteins (HDL) and high concentrations of low-density lipoproteins (LDL)
are associated, in a more or less linear fashion, with cardiovascular disease
such as strokes and heart attacks. It would seem to stand to reason, therefore,
that raising the HDL and lowering the LDL would lead to fewer cardiovascular
“events,” as strokes and heart attacks are called.
One way to achieve this wished-for biochemical change is to treat
patients at risk of such events with niacin, a B vitamin, in addition to the
statins that they are already taking. The largest placebo-controlled trial of
niacin ever undertaken, with 25,673 patients who had already had a stroke or
heart attack, has shown that the addition of niacin, though it does indeed
increase HDL and decrease LDL, has no effect on the rate of heart attack or
stroke. Worse still, it gave rise to serious side effects, such as worsening of
diabetes and unpleasant gastrointestinal, musculoskeletal and dermatological
effects. One of the most unexpected findings of the trial was the excess of
infections in people treated by niacin. If anything, the overall death rate in
the niacin-treated group was higher than that in the placebo control group,
though the difference was not statistically significant (which is not quite the
same thing as saying that it was not real). The patients were followed up, on
average, for nearly four years and at no time was treatment with niacin
superior to that with placebo.
Niacin, though a vitamin, and therefore in the popular imagination
natural and ipso facto good for you, is not only useless in these
circumstances, it seems, but harmful.
The result of the trial was important for itself, for many
patients have been treated with niacin on the grounds that it made “sense” to
do so; but it was also important because it points to a general lesson, namely
that treating statistical markers of disease is not the same as treating
disease itself. This should be obvious, but in practice it isn’t. Doctors
increasingly treat risk factors as if they were disease, with the result that
they could sometimes be doing more harm than good. Of course, there is a long
medical tradition of this.
Furthermore, the trial offers presumptive evidence against the
high-LDL, low-HDL theory of the causation of cardiovascular disease. The
statistical association with these measurements has appeared so strong that the
relationship has been taken as a causative one. But in this trial, treatment
with niacin should have reduced the “event” rate by about 10 percent if the
causative relationship were a true one. It is the contention of those who
oppose the lipoprotein theory of cardiovascular disease that its original
propounders did so, either accidentally or deliberately (though of course they
believe in their hearts that it was deliberately), on the basis of highly
selective data.
Needless to say, believers in niacin could argue that the trial in
the NEJM was one of secondary rather than of primary prevention, that is
to say prevention of further rather than of first cardiovascular events. But it
would be a very brave, not to say foolhardy and indeed unethical investigator
who mounted a trial of niacin in people who had not yet had strokes or heart
attacks, but who for some reason were likely to have one, given the very
considerable harms done to patients by niacin in this trial.
Interestingly, the authors of the report of the trial did not
mention the general lesson which would be profoundly disconcerting for many a
practitioner (to say nothing of his patients).
Theodore Dalrymple, a
physician, is a contributing editor of City Journal and the Dietrich Weismann Fellow at the Manhattan Institute. His new book is Second
Opinion: A Doctor's Notes from the Inner City.
No comments:
Post a Comment