A long-term study from researchers at Johns Hopkins University School of Medicine has found that men's hearts typically grow with age, while women's shrink. The researchers used magnetic resonance imaging (MRI) to study the left ventricle—the main pumping chamber of the heart—in around 3,000 men and women who were enrolled in the Multi-Ethnic Study of Atherosclerosis. All of the participants—who ranged in age from 54 to 94—were free of cardiovascular disease when they entered the study. They had heart scans at the start and 10 years later.

Comparing the MRI scans of men and women, the researchers found that both had declines in left ventricular volume (the amount of blood the chamber holds) over the decade. However, the mass of the ventricle itself increased in men, while it decreased slightly in women. And having a bigger heart seemed to be a disadvantage. It was associated with higher blood pressure and body mass index and lower levels of HDL (good) cholesterol. The study was published online October 20, 2015, by the journal Radiology.

It will take more research to determine what, if anything, this means for women. But it is further evidence that women's hearts are different from men's.