Improving fitness may reverse neurodegeneration in those with mild cognitive impairment, an early stage of Alzheimer's disease, according to a recent study.

Researchers at the University of Maryland found that older adults that improved their fitness through a moderate intensity exercise program increased the thickness of their brain's cortex, the outer layer of the brain that typically atrophies with Alzheimer's disease. These effects were found in both healthy older adults and those diagnosed with mild cognitive impairment (MCI), an early stage of Alzheimer's disease.

"Exercise may help to reverse neurodegeneration and the trend of brain shrinkage that we see in those with MCI and Alzheimer's," Dr. J. Carson Smith, associate professor of kinesiology and senior author of the study, said in a statement. "Many people think it is too late to intervene with exercise once a person shows symptoms of memory loss, but our data suggest that exercise may have a benefit in this early stage of cognitive decline."

For the study, researchers collected and analyzed data previously physically inactive participants, between the ages 61 and 88 years old, were put on an exercise regimen that included moderate intensity walking on a treadmill four times a week over a twelve-week period. On average, cardiorespiratory fitness improved by about 8 percent as a result of the training in both the healthy and MCI participants.

This is the first study to show that exercise and improved fitness can impact cortical thickness in older adults diagnosed with mild cognitive impairment.

The findings are detailed in the Journal of the International Neuropsychological Society.