From the scans, the doctors assessed the size and volume of the participant's left ventricle, and calculated its weight.
Over the study period, the left ventricle in men gained an average of 0.3 ounces (8 grams). In contrast, it lost an average of 0.06 ounces (1.6 grams) in women, the researchers found.
Moreover, the heart's filling capacity (the amount of blood the left ventricle can hold between heartbeats) fell in both sexes. But this was more pronounced in women, with a drop of about 0.4 fluid ounces (13 milliliters), compared to just under 0.3 fluid ounces (10 mL) in men.
These differences emerged even after the researchers controlled for body weight, blood pressure, cholesterol levels, exercise levels and smoking.
These sex-related differences suggest that "men and women may develop disease for different reasons," said lead investigator Dr. John Eng, an associate professor of radiological science at Johns Hopkins. [Don't Sit Tight: 6 Ways to Make a Deadly Activity Healthier]
The findings may help doctors create gender-specific treatments, the researchers said. For instance, cardiologists often prescribe medications that reduce the thickness of heart muscle in people with heart failure. But this treatment might not benefit women as much as it does men, given that women's heart muscle tends to shrink or stay the same size over time, the researchers said.
The study is part of an ongoing, long-term project named the Multi-Ethnic Study of Atherosclerosis (MESA). Researchers plan to continue following the nearly 7,000 people of different ethnic backgrounds who are enrolled, and studying factors that influence these people's heart diseases and failures, the investigators said.
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