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Some
health choices are simplicity itself — eat
more vegetables, don't smoke. But women deciding whether
to try hormone therapy (HT) have to navigate a sea of apparently
conflicting data. Despite the complexities, however, it
is
possible, with enough information, to make a smart choice.
It came as a shock when in July 2002 the Women's Health
Initiative study showed that HT increased the risk of heart
disease — the
No. 1 cause of death in menopausal women. Prior to the
WHI, a randomized controlled study, most of the evidence
on this
issue came from observational studies such as the well-known
Nurses' Health Study (NHS), which found a nearly 50 percent
reduction in heart disease among women taking HT.
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Feb. 7, 2005
The
immediate reaction of many experts was that the WHI had trumped
the NHS and other observational
studies. We think both
the WHI and the NHS (and related studies) may have been right.
How can that be? Except for heart disease, observational studies
and randomized controlled trials have come to nearly identical
conclusions about hormone therapy: HT users have reductions
in rates of colorectal cancer and fractures, and increases
in stroke, invasive breast cancer (especially with combined
estrogen plus progestin therapy), blood clots in the veins
and blood clots in veins that travel to the lungs.
So why the
difference with heart disease? One reason may be the difference
in age of the women in both kinds of studies. The women in
the NHS who used long-term HT had generally begun treatment
as they entered menopause. (The average age at which women
enter menopause in the United States is 51.)
In contrast, the
average age for women in the WHI was 63. Is it plausible that
HT could have beneficial effects on heart disease among women
in their early 50s, yet harmful effects among women a decade
older? We think so, because estrogen has both beneficial and
harmful effects on plaques of atherosclerosis — the cause of
heart attacks.
To appreciate this seeming conundrum, it helps
to understand how heart attacks happen. First, plaques of atherosclerosis
form in the heart's arteries. Each plaque has a cap made of
thin fibers, below which lies the pool of cholesterol. Heart
attacks and many strokes typically occur when the fibrous cap
ruptures, suddenly spilling the cholesterol-rich contents into
the middle of the artery. After that, a blood clot forms and
the artery clamps down — slowing or stopping the flow of blood
to a part of the heart muscle and starving it of the oxygen
and sugar it needs.
Estrogen slows the development of atherosclerotic
plaques, by lowering LDL ("bad") cholesterol and raising HDL
("good") cholesterol levels in the blood — that's good. However,
estrogen may make plaques more likely to rupture by increasing
inflammation within them — that's bad. Thus, it is plausible
that HT might decrease the risk of heart disease in relatively
younger women by slowing the development of plaques, but increase
the risk in relatively older women who already have formed
plaques. Indeed, the results of the WHI suggest that this might
be true. The risk of developing heart disease was lower for
women taking HT at younger ages (although there were too few
women in this group to draw a firm conclusion), but it was
clearly higher for women starting hormones many years after
menopause than for women who did not take hormones.
So what
should a woman do about HT? We think the weight of all current
evidence still argues against recommending the use of HT, other
than short-term use for relieving menopausal symptoms. There
are other ways — including lifestyle changes like exercising,
not smoking and eating healthy — to protect against heart disease.
Komaroff and Grodstein
are from Harvard Medical School and Brigham & Women's Hospital.
© 2005 Newsweek, Inc.
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Menopause