New research shows that old people who lack interest and emotion may have smaller brains, possibly illuminating an overlooked high-risk group for neurological disease.

Dr. Lenore J. Launer, a researcher at the National Institute on Aging and lead author of the study, said the findings indicate smaller brain volume in older people who suffer from apathy but not depression. “Just as signs of memory loss may signal brain changes related to brain disease, apathy may indicate underlying changes," she explained in a press release.

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

The study, which is published in the journal Neurology, surveyed 4,354 people without dementia and with an average age of 76 years. Each subject had their brain scanned with magnetic resonance imaging (MRI) to determine their volume of so-called gray matter and white matter — the two primary types of brain tissue. The researchers also interviewed each subject with questions regarding lack of interest, lack of emotion, reluctance to go outside, and other factors associated with apathy.

They found that people reporting two or more apathy symptoms exhibited 1.4 less gray matter and 1.6 percent less white matter compared to subjects with one or no such symptoms. Notably, excluding people diagnosed with depression did not change these results.

The study dovetail with a recent study from Simon Fraser University in Canada, in which researchers show that the brain appears to slow down by one percent per years after reaching full maturity at age 25. As a result, cognitive skills gradually decline, with losses in concentration and multi-tasking.

Hopefully, the current study will inspire new screening and prevention strategies against neurological disorders like dementia, which are expected to become more and more prevalent over the next few decades. "If these findings are confirmed, identifying people with apathy earlier may be one way to target an at-risk group," Launer told reporters.