The study of older adults at increased risk for Alzheimer's disease shows that moderate physical activity may protect brain health and stave off shrinkage of the hippocampus.
Dr J Carson Smith, a kinesiology researcher in the University of Maryland School of Public Health who conducted the study, said that while all of us will lose some brain volume as we age, those with an increased genetic risk for Alzheimer's disease typically show greater hippocampal atrophy over time.
"The good news is that being physically active may offer protection from the neurodegeneration associated with genetic risk for Alzheimer's disease," Smith said.
"We found that physical activity has the potential to preserve the volume of the hippocampus in those with increased risk for Alzheimer's disease, which means we can possibly delay cognitive decline and the onset of dementia symptoms in these individuals.
"Physical activity interventions may be especially potent and important for this group," Smith added.
Smith and colleagues, including Dr Stephen Rao from the Cleveland Clinic, tracked four groups of healthy older adults ages 65-89, who had normal cognitive abilities, over an 18-month period and measured the volume of their hippocampus (using structural magnetic resonance imaging, or MRI) at the beginning and end of that time period.
The groups were classified both for low or high Alzheimer's risk (based on the absence or presence of the apolipoprotein E epsilon 4 allele) and for low or high physical activity levels.
Of all four groups studied, only those at high genetic risk for Alzheimer's who did not exercise experienced a decrease in hippocampal volume (3 per cent) over the 18-month period.
All other groups, including those at high risk for Alzheimer's but who were physically active, maintained the volume of their hippocampus.
"This is the first study to look at how physical activity may impact the loss of hippocampal volume in people at genetic risk for Alzheimer's disease," said Dr Kirk Erickson, an associate professor of psychology at the University of Pittsburgh.
"There are no other treatments shown to preserve hippocampal volume in those that may develop Alzheimer's disease.
"This study has tremendous implications for how we may intervene, prior to the development of any dementia symptoms, in older adults who are at increased genetic risk for Alzheimer's disease," Erickson said.
The findings are published in the journal Frontiers in Aging Neuroscience.