Older people who show signs of apathy but not depression may have smaller brains than those who don't have apathy.

"Just as signs of memory loss may signal brain changes related to brain disease, apathy may indicate underlying changes," Lenore J. Launer, PhD, with the National Institute on Aging at the National Institutes of Health (NIH) 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. And the fact that participants in our study had apathy without depression should turn our attention to how apathy alone could indicate brain disease."

Loss of brain volume is a sign of aging, but large amounts of volume loss can be an indicator of brain disease, an American Academy of Neurology (AAN) news release reported. 

The researchers conducted MRIs on 4,354 people with an average age of 76. The participants also answered questions that tested their apathy symptoms. 

These symptoms included "lack of interest, lack of emotion, dropping activities and interests, preferring to stay at home and having a lack of energy," the news release reported. 

The team found those with apathy symptoms had 1.4 percent smaller gray matter volume 1.6 percent less white matter volume than those who had less than two of the listed symptoms. 

Gray matter is responsible for learning and memory while white matter acts as the "communication cables that connect different parts of the brain," the news release reported. 

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

"The study was supported by the National Institutes of Health, the National Institute on Aging, the Icelandic Heart Association and the Icelandic Parliament," the news release reported.