Compared to sedentary peers, the older adults in the study who were active had better heart-rate variability a measure of the slight differences in time between each heartbeat that is influenced by the health of both the heart and the nervous system.
Modest physical activity, such as the distance and pace of walking, is important for the hearts electrical well being of older adults, Luisa Soares-Miranda told Reuters Health in an email.
The effects were seen over time, added Soares-Miranda, a researcher at the Harvard School of Public Health in Boston and the Faculty of Sport at the University of Porto in Portugal who led the new research.
In our study, older adults that increased their walking pace or distance had a better heart rate variability when compared with those that decreased their walking pace or distance, she said.
Heart rate variability is a sign of a healthy heart that can respond readily to changing demands and is often used as a measure of fitness for adults of any age.
Previous research has shown a link between exercise, heart rate variability, and lowered cardiovascular risk in groups of middle-aged people, but little is known about whether those ties persist in older adults, the researchers note in the journal Circulation.
Soares-Miranda and her colleagues analyzed data on nearly 1,000 participants in the Cardiovascular Health Study that began in the U.S. in 1989. The men and women were 65 or older at the beginning of the study and were followed for five years.
Study participants were initially evaluated for their health status, medical history and cardiovascular risk factors, and asked about their usual amounts of physical activity, including sports and everyday activities such as gardening, housework and walking.
All the people included in the new analysis had their heart rate variability tested at the beginning and end of the five-year study period.
When the researchers analyzed the data, they divided participants into five groups representing the lowest to the highest amounts of physical activity and found that people in the top fifth also had the most favorable heart-rate variability results.
That was particularly true for those who increased their walking pace or distance over the five years studied.
The results dont prove that the exercise influenced heart rate variability, but the researchers adjusted for several factors, including weight, overall health, use of heart drugs or presence of diabetes, to see if people with the healthiest hearts were the most likely to engage in physical activity.
The results held, and based on other large studies, Soares-Miranda and her team calculated that participants who were the most active had about 11 percent less risk of cardiovascular disease compared to participants who were the least active.
Our results suggest not only that regular physical activity later in life is beneficial, but also that certain beneficial changes that occur may be reduced when physical activity is reduced, Soares-Miranda said.
She also said the study findings support the need to maintain modest physical activity throughout the aging process.
Even small increases can lead to a better health, while reducing physical activity has the opposite effect, she said. So, any physical activity is better than none, and more is better.
Walking is the most common form of activity, Soares-Miranda said, and she believes its a good way to achieve physical activity recommendations for aerobic exercise.
I think that if a senior feels comfortable with his or her usual physical activity -- independently of what the activity is, he or she should not slow down, Soares-Miranda said. If walking is the main physical activity, try to walk an extra block or walk at a faster pace. It is never too late to start and to do more.
Dr. Michael Rich said that normal heart rate variability typically declines with age and can be partly due to diseases people develop or to physical deconditioning.
Rich is director of the Cardiac Rapid Evaluation Unit of the Barnes-Jewish Hospital in St. Louis and was not involved in the new research.
I think what this study shows is that despite what we know about changes in heart rate variability with age, there still is an association between physical activity and heart rate variability that is favorable and that people who exercise regularly have a more favorable profile of different heart rate variability, he told Reuters Health.
What the authors are trying to imply, but cant actually prove in this study, is that the favorable effect of exercise on heart rate variability might be part of the mechanism for or at least contribute to the general association between good physical conditioning, regular physical activity and health in general, and risk for cardiovascular diseases in particular, such as heart attack, and congestive heart failure, he said.
Rich, who is a cardiology researcher with Washington University in St. Louis and a spokesperson for the American Geriatrics Society, added that more research on the oldest seniors would be beneficial.
The average age of the population of this study was 71, so it's a relatively young older population and whether the findings are applicable in people over 80, I think we don't know from the study, he said. It would be interesting to do a similar type of analysis on a population of people over the age of 80.