In a new study published in the journal NeuroImage, an international team of researchers examined the effects of aerobic exercise on a region of the brain called the hippocampus, which is critical for memory and other brain functions.
Brain health decreases with age, with the average brain shrinking by approximately 5% per decade after the age of 40.
Studies in mice and rats have consistently shown that physical exercise increases the size of the hippocampus but until now evidence in humans has been inconsistent.
In the new study, lead author Dr. Joseph Firth, a postdoctoral research fellow at the National Institute of Complementary Medicine at Western Sydney University, Australia, and colleagues reviewed 14 clinical trials which examined the brain scans of 737 people before and after aerobic exercise programs or in control conditions.
The participants’ mean age in the included trials ranged from ranged from 24 to 76 years.
Four trials recruited participants with a diagnosis of schizophrenia or other psychotic disorders, six recruited healthy older adults, whilst individual studies examined the effects of exercise of hippocampal volumes in people with depression, mild cognitive impairment, probable Alzheimer’s disease, and healthy young-middle aged adults.
The researchers examined effects of aerobic exercise, including stationary cycling, walking, and treadmill running.
The length of the interventions ranged from three to 24 months with a range of 2-5 sessions per week.
Overall, the results showed that, while exercise had no effect on total hippocampal volume, it did significantly increase the size of the left region of the hippocampus in humans.
“Our study provides some of the most definitive evidence to date on the benefits of exercise for brain health,” Dr. Firth said.
“When you exercise you produce a chemical called brain-derived neurotrophic factor, which may help to prevent age-related decline by reducing the deterioration of the brain.”
“Our data showed that, rather than actually increasing the size of the hippocampus per se, the main ‘brain benefits’ are due to aerobic exercise slowing down the deterioration in brain size. In other words, exercise can be seen as a maintenance program for the brain.”
“Along with improving regular ‘healthy’ aging, the results have implications for the prevention of aging-related neurodegenerative disorders such as Alzheimer’s and dementia — however further research is needed to establish this.”
Joseph Firth et al. 2018. Effect of aerobic exercise on hippocampal volume in humans: A systematic review and meta-analysis. NeuroImage 166: 230-238; doi: 10.1016/j.neuroimage.2017.11.007