During menopause, women can experience a range of symptoms including hot flashes, night sweats, fatigue, and vaginal dryness.

Hormone replacement therapy (HRT), also referred to as estrogen replacement therapy, is widely used to counter these side effects.

Because HRT is so commonly used, it has received a great deal of attention from researchers. Benefits have been weighed against concerns and scientific opinion has shifted.

On the positive side, HRT has been found to lower the risk of osteoporosis and improve certain measures of heart health.

Conversely, other studies have demonstrated a link between HRT and an increased risk of cancer and stroke.

Concerns surrounding these risks have created a sharp decline in the number of women using HRT over the past 15 years.

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Reopening the HRT debate

A new study, being presented on March 17 at the American College of Cardiology’s 66th Annual Scientific Session & Expo in Washington, D.C., might nudge public opinion back the other way.

The study is titled “Hormone replacement therapy is associated with less coronary atherosclerosis and lower mortality” and it’s guaranteed to spark discussion.

The researchers looked retrospectively at the data of more than 4,200 women who received a coronary calcium scan at Cedars-Sinai Medical Center in Los Angeles between 1998 and 2012.

A coronary calcium scan measures calcium buildup in coronary arteries. Higher calcium levels are a marker for plaque buildup and, consequently, signal an increased risk of heart attack or stroke.

Of the participants included, 41 percent were using HRT at the time of their scan.

HRT use was at its highest between 1998 and 2002 and slowly declined across the study period, dropping from 60 percent in 1998 to 23 percent in 2012.

Around 6 percent of the women died during the study follow-up, which spanned an average of eight years.

During the analysis, the data were adjusted for coronary calcium score, age, and a range of cardiovascular risk factors, such as diabetes, high cholesterol, and high blood pressure.

Because those in the HRT group were older than those in the non-HRT group (64 versus 60, respectively), the researchers also adjusted for this discrepancy.

Once all variables were accounted for, the team found that women using HRT were 30 percent less likely to die than those not taking the medication.

Similarly, women on HRT were 20 percent more likely to have a zero score on the coronary calcium scan - the lowest possible score, indicating minimal heart attack risk.

They were also 36 percent less likely to have a coronary calcium score above 399 - a score linked with severe atherosclerosis and high heart attack risk.

The researchers’ conclusions are clear, but they also call for caution. Dr. Yoav Arnson, a visiting postdoctoral scientist at Cedars-Sinai and lead study author, says:

“Hormone replacement therapy resulted in lower atherosclerosis and improved survival for all age groups and for all levels of coronary calcium. From this, we do think it is beneficial, but we would need prospective or randomized studies to determine which groups might not benefit or even be harmed by this therapy.”

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The protective abilities of HRT

This large-scale study provides evidence that HRT exerts a protective effect on cardiovascular health, but how might this work?

Estrogen’s positive influence on heart health involves at least two pathways.

First, estrogen reduces levels of low-density lipoprotein, or “bad,” cholesterol, and increases high-density lipoprotein, or “good,” cholesterol. Secondly, estrogen increases flexibility in blood vessels and arteries, helping them to cope with changes in flow.

Before menopause, women have high levels of estrogen in their systems and, typically, have levels of cardiovascular health equivalent to that of men 10-20 years younger than them.

However, after menopause, estrogen levels plummet and heart disease risk increases as a result.

HRT replaces this lost estrogen, reinstating its protective abilities.

Although the current study is large and has a longer-than-average follow-up time, it does not reveal the specific groups of women that might benefit from the treatment.

It also doesn’t add to the understanding of other risks associated with HRT, such as cancer.

Though the current findings come down heavily in favor of HRT, a decision to begin treatment will still be a complex choice for an individual and their doctor to make.

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