The results have implications for the prevention and treatment of diseases such as Alzheimer’s and dementia, the researchers say.
They found that aerobic exercise in humans led to an actual increase in the size of the left hippocampus region of the brain which is critical for memory and other brain functions.
Although the total volume of the hippocampus did not increase, exercise helped slow down the deterioration of the brain.
Brain health decreases with age, with the average brain shrinking by approximately five per cent per decade after the age of 40.
The team from Australia’s National Institute of Complementary Medicine at Western Sydney University and the Division of Psychology and Mental Health at the University of Manchester reviewed 14 clinical trials which examined the brain scans of 737 people.
The study, published in the journal NeuroImage, included a mix of healthy adults, people with mild cognitive impairment such as Alzheimer’s and people with a clinical diagnosis of mental illness including depression and schizophrenia.
They were aged 24 to 76 years with an average age of 66 and either had aerobic exercise programmes or control conditions.
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.
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.
The study showed that aerobic exercise can improve memory function and maintain brain health as we age.
Lead author, NICM postdoctoral research fellow, Joseph Firth said the study provides some of the most definitive evidence to date on the benefits of exercise for brain health.
He said: “When you exercise you produce a chemical called brain-derived neurotrophic factor (BDNF), 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.”
He added: “Along with improving regular ‘healthy’ ageing, the results have implications for the prevention of ageing-related neurodegenerative disorders such as Alzheimer’s and dementia.
“However further research is needed to establish this.
“Interestingly, physical exercise is one of the very few ‘proven’ methods for maintaining brain size and functioning into older age.”