They say you're only as old as you feel. Now, new research suggests that there may be some truth to the expression, finding that those who feel younger than their age actually do show fewer signs of brain aging.

Carried out by researchers at Seoul National University in Korea, the new small-scale study looked at whether how old we feel -- also called our subjective age -- does reflect how our bodies are aging.

"Why do some people feel younger or older than their real age?" asks Dr. Jeanyung Chey. "Some possibilities include depressive states, personality differences or physical health. However, no one had investigated brain aging processes as a possible reason for differences in subjective age."

For the research the team recruited 68 healthy people aged 59 to 84 and gave each person MRI brain scans in order to assess the volume of gray matter in various brain regions.

Participants were also asked to complete a survey which assessed their cognitive abilities and perceptions of their overall health and asked whether they felt older or younger than their age.

The results showed that participants who felt younger than their age were more likely to score higher on a memory test, reported better health and were less likely to report symptoms of depression.

In addition, those who felt younger than their age also showed increased gray matter volume in key brain regions.

"We found that people who feel younger have the structural characteristics of a younger brain," said Chey. "Importantly, this difference remains robust even when other possible factors, including personality, subjective health, depressive symptoms, or cognitive functions, are accounted for."

The study is the first to find a link between subjective age and brain aging, with the team hypothesizing that those who feel older may be able to feel the aging process in their brain, as their loss of gray matter may make cognitive tasks more challenging.

Another possibility is that those who feel younger than their age are more likely to lead a more physically and mentally active life, which could cause improvements in brain health, while for those who feel older, the opposite could be true.

"If somebody feels older than their age, it could be sign for them to evaluate their lifestyle, habits and activities that could contribute to brain aging and take measures to better care for their brain health," said Chey.

The results can be found published online in the journal Frontiers in Aging Neuroscience.