For decades, medical professionals and researchers have commonly accepted that postmenopausal women have a higher risk of developing heart disease than premenopausal women. But it’s hard to pinpoint exactly what the cause of this pattern is.

“Men have always been included in studies and so we know a lot about men, but women are less likely to be studied,” says Yvonne van der Schouw, professor of chronic disease epidemiology at the University Medical Center Utrecht in the Netherlands. “It’s partly because you don’t want to test drugs on someone who could become pregnant during the trials.”

Van der Schouw’s own research focuses on the association between menopause and heart disease risk. One consequence of lower inclusion of women in medical studies compared to men is that we know less about the postmenopausal heart disease phenomenon than perhaps we should, she says.

A Study of Omani Women

Saleh wants to use her science to change this.

She has taken blood samples from 413 Omani women from ages 18 through 80 plus. The sample was split roughly into thirds. One third of the participants were premenopausal, another third were currently going through menopause and the final third were postmenopausal.

The premenopausal participants had their blood samples taken within three days of the beginning of their menstrual cycle. “Previous studies have shown this is when they are most likely to be biochemically similar to postmenopausal women,” explains Saleh. “It means that we’re comparing apples with apples, and not apples with pears.”

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Saleh then conducted an analysis of the blood samples, looking for chemical signals of heart disease risk factors—such as an amino acid called homocysteine, retinal binding proteins and lipid levels in general. High levels of these various molecules would indicate a higher risk of developing heart disease.

Additionally, she took body mass index (BMI) ratings and measured the waist sizes and waist-to-hip ratios of the participants. These measures are commonly used as indicators of the amount of visceral fat—that’s fatty tissue deeper in the body rather than fat just below skin level.

The results showed, as expected, that the postmenopausal women had higher levels of homocysteine, retinal binding proteins and lipids. But additionally, the data showed there was a high association between these risk factors and the amount of visceral fat.

“This is the first study showing this in the Middle East,” says Saleh. “It shows that visceral fat is the biggest problem.”

Female hormones such as oestrogen have a protective effect on fat distribution. Postmenopausal women produce lower levels of these hormones, and that could offer an explanation for Saleh’s findings. “I wouldn’t recommend hormone supplements because they can have a cancer risk,” says Saleh. “Let’s target the visceral fat with exercise, balanced diet and cutting back the snacks.”

Why Larger Studies Are Needed

These findings are not the final and definitive answer to the question of why so many women die of heart disease after menopause, but the research does add to a growing body of literature, which collectively could one day help researchers to better explain the phenomenon.

In the meantime, research like Saleh’s is a pursuit worth following, says van der Schouw.

“It’s important to know what is causing this because if we know the biological mechanism then we might come up with an intervention,” she says. “It will take time, but I do think we’ll eventually figure it out. We need more and larger studies.”

That said, research of this nature is not without its limitations. It’s so hard to properly unpick the effect of age from the results of studies like Saleh’s. Postmenopausal women are likely to be aged 50 and up, so maybe it’s just old age that’s responsible for the higher risk of heart disease.

Saleh did take age into account in conducting her statistical breakdown, and the age spread of her participants certainly helps, but it’s never possible to completely eradicate the influence of old age. That’s why van der Schouw is in favor of larger studies—those with tens of thousands of participants—because it makes it easier to reduce the confounding effect of age.