Women's and men's hearts work differently. That's perhaps most clear, though not well-known enough, in heart attacks: while men tend to have the stereotypical chest-clutching pain, women can experience more subtle symptoms that risk being overlooked.
A new study published in the journal Radiology presents further evidence for cardiac sex differences. Based on MRI scans, researchers led by Johns Hopkins University's Dr. John Eng found that the heart ages differently in men and women.
In a phone call, Eng explained that previous research had shown that the heart changes in volume and weight, and that these changes are related to heart failure, so they wanted to do a longitudinal study (following the same people over a period of time) to see what they could observe. The sex difference they saw in their data poses many new questions, including whether or not men and women should be treated differently for heart failure.
"In the past, cardiovascular studies have been mostly done on men"
"The implication of that is that it may be that the heart ages differently in men and women and that treatments related to the shape changes may have to be different—like treatment for heart failure might have to be different for men and women," said Eng. "It's the first time we've made this observation so it's going to require more research to try to understand what the cause of that is and whether it translates into a need for treating the patients differently."
The study used MRI scans to look at the hearts of almost 3,000 people over an average time difference of 9.4 years. It's part of a broader medical study called the Multi-Ethnic Study of Atherosclerosis (MESA), which includes over 6,000 men and women of different ethnic backgrounds.
In both sexes, the volume of the left ventricle—a chamber of the heart that pumps blood around your body—decreased with age, but more so for women (13 millileter decrease for women versus 10 mL for men). Meanwhile, in men, the mass of the left ventricle increased by an average of eight grams. But in women, it decreased by 1.6 g.
The weakening of the left ventricle is known as a major cause of heart failure, but the physiological changes found in the study suggest the problem is more complex than previously thought. While Eng qualified that many other factors can impact the heart as it ages, the study shows the importance of considering sex differences in medical research, particularly when it relates to such a widespread and serious condition as heart failure.
Studies routinely fail to take potential differences in male and female biology into account—often simply because they don't collect data on sex or only study men. Last year, the National Institutes of Health announced policies to require researchers it funds to also use male and female cells and animals in studies, on top of previous requirements to include women in clinical trials.
Eng agreed that it was important to include both sexes. "I think it is," he said. "This MESA study, where this data came from, was designed to look at an equal number of men and women—in the past, cardiovascular studies have been mostly done on men."
Further work is needed to try to figure out why men and women's hearts age differently, and what the implications are on our understanding of age-related heart failure and its treatments.