New York, Oct 20 (IANS): In men the heart muscle that encircles the main heart chamber grows bigger and thicker with age, while in women, it retains its size or gets somewhat smaller, reveals a new study of the ageing hearts of nearly 3,000 adults.

In both sexes, the heart chamber, the left ventricle -- which fills with blood and then forces it out -- gets smaller with time, found the study, which analysed MRI scans of the hearts of nearly 3,000 adults.

As a result, less blood enters the heart and less gets pumped out to the rest of the body.

Results of the research, led by Johns Hopkins University scientists, do not explain exactly what causes the sex-based differences but they may shed light on different forms of heart failure seen in men and women that may require the development of gender-specific treatments, the scientists said.

"Our results are a demonstration of the concept that heart disease may have different pathophysiology in men and women, and of the need for tailored treatments that address such important biologic differences," said senior study author professor Joao Lima from Johns Hopkins School of Medicine.

Previous studies have assessed heart changes over time using ultrasound, but, the researchers said, MRI scans tend to provide more detailed images -- and more reliable information -- about the structure and function of the heart muscle.

"Thicker heart muscle and smaller heart chamber volume portend heightened risk of age-related heart failure but the gender variations we observed mean men and women may develop the disease for different reasons," said lead investigator John Eng.

A condition that affects more than five million Americans, heart failure, is marked by the gradual "floppiness" and weakening of the heart muscle and eventual loss of pumping ability.

The study was published online in the journal Radiology.