Based on a review of studies on exercise and its effect on brain functioning in human and animal populations, researchers find that physical exercise may slow aging's effects and help people maintain cognitive abilities well into older age. Animals seem to benefit from exercise too and perform spatial tasks better when they are active. Furthermore, fitness training -- an increased level of exercise -- may improve some mental processes even more than moderate activity, say the authors of the review.
Findings from the review will be presented at the 114th Annual Convention of the American Psychological Association (APA).
Varying opinions still exist on the benefits of exercise and activity, said authors Arthur F. Kramer, PhD, Kirk I. Erickson, PhD and Stanley J. Colcombe of the University of Illinois at Urbana -- Champaign, "but our review of the last 40 years of research does offer evidence that physical exercise can have
a positive influence on cognitive and brain functions in older animal and human subjects." Different methodologies were examined to comprehensively study what effects exercise can have.
The researchers first examined the epidemiological literature of diseases to determine whether exercise and physical activity can at certain points in a person's lifetime improve cognitive ability and decrease the likelihood of age-related neurological diseases, like Alzheimer's. The authors then reviewed longitudinal randomized trial studies to see if specific fitness training had an affect on cognition and brain function in older adults. Finally, animal studies were examined to understand the molecular and cellular mechanisms responsible for exercise effects on the brain as well as on learning and memory.
Based on a review of the epidemiological literature, the authors found a significant relationship between physical activity and later cognitive function and decreased occurrence of dementia. And the benefits may last several decades. In a few of the studies that examined men and women over 65 years old, the findings showed that those who exercised for at least 15-30 minutes at a time three times a week were less likely to develop Alzheimer's Disease, even if they were genetically predisposed to the disease.
By examining the human intervention studies, a relationship was also found between fitness training and improved cognition, more efficient brain function and retained brain volume in older people, said Kramer. He cautions that different fitness training regimens and aspects of mental functions need further study to solidify a causal relationship. But, he added, there are some preliminary positive findings. In a four year study looking at the relationship between physical activity on cognition and brain function in 62-70 year olds, "those who continued to work and retirees who exercised showed sustained levels of cerebral blood flow and superior performance on general measures of cognition as compared to the group of inactive retirees," said Kramer.
Other studies confirmed the evidence that fitness does have positive effects on brain function in older adults. A study of older adults who were randomly assigned to either a walking group or a stretching and toning control group for six months found that those in the walking group were better able to ignore distracting information in a distractibility task than those in the control group. "Aerobically trained older adults showed increased neural activities in certain parts of the brain that involved attention and reduced activity in other parts of the brain that are sensitive to behavioral conflict," said Kramer.
Animal studies also provide support for the aging benefits of physical activity. Analyzing the effects of exercise in animal populations provides a unique window into learning about exercise-induced neurological and cognitive plasticity -- the ability of parts of the brain to function in place of other parts of the brain, said Dr. Kramer. Some of the animal studies reviewed used voluntary-wheel running experiments to show the existence of performance benefits of wheel running on hippocampus-related spatial learning tasks. Moreover, a few studies found that aged rodents that exercised in a water maze learned and retained information about a hidden platform better than age-matched controls.
Exercise also protected both young and aged animals from developing some age-related diseases as indicated by increases in certain neurochemical levels that can offset or prevent certain pathological diseases.
"From this review we have found that physical and aerobic exercise training can lower the risk for developing some undesirable age-related changes in cognitive and brain functions," said Dr. Kramer, "and also help the brain maintain its plasticity - ability to cover one function if another starts failing later in life."
More research is needed to know exactly how much and what types of exercise produce the most rapid and significant effects on thinking and the brain; how long exercise effects last following the end of training; or how much exercise is needed to get continued benefits, said Kramer.
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