Physical activities such as walking helps older adults lessen age-related decline in brain structure, says a new research.

The researchers found the relationship between fitness and brain structure only in older adults, but not younger adults.

"We found that higher levels of cardiorespiratory fitness were associated with enhanced brain structure in older adults," explained study author Scott Hayes, assistant professor of psychiatry at Boston University School of Medicine.

"We found that physical activities that enhance cardio-respiratory fitness, such as walking, are inexpensive, accessible and could potentially improve quality of life by delaying cognitive decline and prolonging independent function," he noted.

Cardio-respiratory fitness refers to the ability of the circulatory and respiratory systems to supply oxygen to skeletal muscles during sustained physical activities.

For the study, the researchers compared younger adults (age 18-31) to older adults (age 55-82). All participants had magnetic resonance imaging (MRIs) taken of their brains and their cardiorespiratory (heart and lung) fitness was measured while they exercised on a treadmill.

The researchers found cardio-respiratory fitness was positively linked to the structural integrity of white matter fiber bundles in the brain in the older adults, while no such association was observed in younger adults.

"We hope this study provides additional motivation for older adults to increase their levels of physical activity, which positively impacts health, mood, cognition and the brain," Hayes said.

The findings appeared online in the journal Annals of Clinical and Translational Neurology.