Feelings of apathy in older adults who are otherwise not suffering depression may indicate their brains are shrinking, according to a new study.

Apathy is a lack of interest or emotion and "just as signs of memory loss may signal brain changes related to brain disease, apathy may indicate underlying changes," study lead Lenore J. Launer, a researcher with the National Institute on Aging at the National Institutes of Health in Bethesda, MD, and a member of the American Academy of Neurology, said in a news release.

"Apathy symptoms are common in older people without dementia," she said "The fact that participants in our study had apathy without depression should turn our attention to how apathy alone could indicate brain disease."

The findings from the research conducted by Launer and her science team were published in the April 16 online issue of Neurology, the medical journal of the American Academy of Neurology.

Launer's team looked to brain mass as a measure of accelerated brain aging.

The loss of some brain volume is a typical condition of aging, said Launer, but in the study, larger volume losses suggested brain diseases.

The research asked 4,354 older people with an average age of 76 years, but without any signs of dementia, to undergo magnetic resonance imaging (MRI) scans.

The experiment subjects were also asked a series of questions designed to measure symptoms of apathy, which include lack of interest, lack of emotion, lack of energy, dropping activities and interests, and a preference to stay home, away from the outside world.

People with two or more apathy symptoms had 1.4 percent smaller gray matter volume and 1.6 percent less white matter volume, as compared to others who had less than two apathy symptoms, according to the paper.

Gray matter, the researchers explained, is where learning takes place and memories are stored in the brain. White matter acts as the communication cables that connect different parts of the brain.

"If these findings are confirmed," said Launer, "identifying people with apathy earlier may be one way to target an at-risk group."