Men’s and women’s hearts age differently, scientists have just learned.
This revelation is prompting physicians to think differently about ways to treat heart disease.
The most surprising discovery in a new 10-year study at Johns Hopkins University School of Medicine is that men and women both experience decreases in the volume of the left ventricle, the heart’s main pumping chamber.
However, in men, the muscle mass of the left ventricle increases — a condition called hypertrophy — while in women it decreases.
These findings were made with MRI. The results were published online today in the journal Radiology, from the Radiological Society of North America.
Watching the Heart Age
Earlier studies have also revealed increases and decreases in left ventricular mass as people age.
Those studies, however, were often cross-sectional. They examined one point in time and compared young and old patients without looking at differences in lifestyle and other aspects of personal history.
For this latest study, Dr. John Eng, an associate professor of radiology and radiological science, and his fellow researchers explored long-term changes in the same group of people. The scientists first acquired data from a patient’s baseline cardiac MRI and then compared it with another MRI 10 years later.
“We had the opportunity to re-examine the same people after 10 years, so we could see what happened to their hearts after a decade,” Eng told Healthline. “This is a more reliable way to assess left ventricular changes over time.”
The project, called the Multi-Ethnic Study of Atherosclerosis (MESA), was a large observational study focused on cardiovascular disease. The team studied the left ventricles of 2,935 people.
Participants were free of clinical cardiovascular disease at the beginning of the study in 2000 to 2002. The follow-up MRIs were done between 2010 and 2012 with a median interval of 9.4 years from the baseline. At the second MRI, participants ranged in age from 54 to 94.
Smaller scale follow-ups occurred between those years, Eng said, and continue to occur today.
The shape of the heart changes over time in both men and women, Eng said, but the patterns of change are different.
“Men's hearts tend to get heavier and the amount of blood they hold is less, while women's hearts don't get heavier,” he said.
Study Results Were Surprising
When Eng and his colleagues looked at their data, “We suspected we would find differences between men and women, but the pattern is more striking than we would have guessed.”
The team is looking at one theory about these gender differences.
“Any statement regarding the cause of the differences we observed would be speculative,” Eng said. “One hypothesis we are considering is that the differences are related to sex-specific variations in diffuse myocardial fibrosis that we have observed in other MRI studies.”
Myocardial fibrosis is the replacement of heart muscle with fibrous connective tissue that interferes with contraction of the remaining heart muscle, Eng said. Advances in MRI technology, however, can detect the condition before it becomes obvious.
With these newly discovered gender differences in how hearts age, what should men and women do differently?
“Men and women should watch their blood pressure very closely,” Dr. Joao Lima, a professor of medicine, radiology, and epidemiology at Johns Hopkins, and one of Eng’s project colleagues, told Healthline. “But, given that men are prone to develop heart disease earlier, they should be particularly aggressive.”
The project highlighted the advantages of cardiac MRI in measuring left ventricular mass.
“Measurements of mass and volume can be made directly from MRI images,” Eng said. “Mass and volume can also be estimated from echocardiography, which is used in most heart imaging. But typically these estimates involve equations that make geometric assumptions about the shape of the heart, so these estimates are not as accurate as MRI.”
Although echocardiography is not as precise as MRI, cardiologists still use it.
“Echocardiography is less expensive and less technically challenging,” Eng said. “In current clinical practice, precise measurements of mass and volume are usually not necessary to guide clinical decision-making.”
The researchers will follow up periodically with study participants by phone, Eng said, because there is currently no funding available to conduct another round of physical exams and cardiac MRIs.
Factors That Cause Heart Problems
What causes a left ventricle to thicken?
Eng said that blood pressure is the biggest culprit.
“If a person has high blood pressure,” he said, “ventricle walls may thicken from having to work harder to pump blood.”
Problems with heart valves also hinder ventricular function, he added.
Lima said weight is another problem.
“Overweight and obesity lead to heart hypertrophy, and both men and women should pay a lot of attention to that,” he said.
The researchers said the study appears to confirm the importance of blood pressure and diet to cardiac health. Increased left ventricular mass was associated not only with higher blood pressure but also with body mass index, they wrote.
Lima added: “There was less increase in left ventricular mass in participants who had hypertension that was treated or had higher levels of high-density lipoprotein, or HDL, cholesterol,” the so-called “good” cholesterol that helps reduce the risk of heart disease.
What makes this research unique, Eng said, is: “We believe ours is the first study to perform baseline and follow-up cardiac MRI exams on a large sample of participants. Longitudinal studies have been done with echocardiography, but more precise measurements of the heart can be made with MRI.”
MRI, however, was only part of the equation.
“The MESA study population underwent comprehensive physical examinations and questionnaires covering a wide variety of potential cardiac risk factors,” Eng said. “Our study focused on ‘traditional’ risk factors.”
The MESA study also collected data on many other aspects related to cardiovascular health. These included diet, sleep, exercise, cognitive ability, and calcium deposits in various arteries. Those factors have been, and will be, the subject of other research articles, Eng said.