Vigorous Walking May Slow Biological Aging to a Crawl

By Todd Neale
TORONTO, April 10 2008-- Vigorous walking for about an hour a day five times a week can chop a dozen years off the biological age of persons 64 and older, according to a researcher here.A review of recent studies in patients age 64 and older showed that such a regimen can boost maximal oxygen intake by about 25% within three months, effectively decreasing biological age by about 12 years, Roy Shephard, M.D., Ph.D., of the University of Toronto, reported online in the British Journal of Sports Medicine.This could also extend a patient's functional independence -- which is likely lost when maximal oxygen intake drops below 18 mL/kg/min for men and 15 mL/kg/min for women -- by about the same amount of time, he said.
The benefits of aerobic exercise increase the longer it is performed, he said.
"There remains a need to clarify the importance of deteriorations in fitness relative to other potential causes of dependency," he wrote, "but, from the practical viewpoint, regular aerobic activity can address many of the issues of both functional loss and chronic disease."
Past studies by Dr. Shephard suggested that keeping up aerobic fitness could stem the onset of dependency in older patients by maintaining functional capacity.
A program of endurance training could offset the expected loss of 5 mL/kg/min in maximal oxygen intake per decade, which equates to about 10 years of biological age, he said.
To assess the current state of knowledge on the subject, Dr. Shephard reviewed 30 studies published since 1990.
There was some uncertainty in the findings about the rate of decline of maximal oxygen intake in older patients.
The use of different study designs -- longitudinal or cross-sectional -- and the fact that most data were collected from relatively healthy participants made it difficult to compare the data.
"There is thus some inter-observer disagreement on the rate of deterioration during the retirement years," he wrote, "but is seems reasonable to postulate that a loss of at least 4 to 5 mL/kg/min per decade continues into advanced old age."
As maximal oxygen intake dropped through the years, the amount of activity a patient could participate in without becoming fatigued declined until functional independence was lost.
In one cross-sectional study, researchers found that the risk for dependency was increased by 14% for each 1 mL/kg/min loss in maximal oxygen intake in patients ages 55 to 86.
However, Dr. Shephard wrote, it remains difficult to determine how much of the risk of dependency comes from a reduction of aerobic fitness because, in most studies, few of the participants beginning a trial complete it, and those that do are generally more healthy.
The studies reviewed showed a trend toward greater gains in aerobic fitness with a longer training regimen. Average gains were 12.9% in an eight- to 10-week program, 14.1% in a 12- to 18-week program, and 16.9% with 24 to 52 weeks of training.
Those studies that used a high-intensity regimen reached the gains of 25%, which equals an increase in maximal oxygen intake of 6 mL/kg/min or a decrease of about 12 years of biological age.
Dr. Shephard noted that aerobic fitness may indirectly delay dependency by preventing other conditions that are likely to diminish functional capacity, including obesity, diabetes, hypertension, myocardial infarction, stroke, some forms of cancer, and osteoporosis.
Exercise also hastens recovery from injuries and any additional muscle power may prevent falls, he said.
"There seems good evidence that the conservation of maximal oxygen intake increases the likelihood that the healthy elderly person will retain functional independence," he said.
After completing the review, Dr. Shephard said that there is still missing information on how much aerobic fitness contributes to continuing independence in older patients.
He said that further research needs to focus on which services or changes in the home can postpone institutionalization in a cost-effective manner.
Dr. Shephard declared no competing interests.
Primary source: British Journal of Sports MedicineSource reference:Shephard R, "Maximal oxygen intake and independence in old age" Br J Sports Med 2008; DOI: 10.1136/bjsm.2007.044800.