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"We're not talking about seniors trying to run half-marathons. We're talking about the impact of much more typical and achievable behavior among older individuals, like walking five times a week for 30 minutes or more, and other kinds of similar leisure-type activities," said study lead author Dr. Christopher deFilippi, of the University of Maryland School of Medicine at Baltimore.
A simple blood test can detect levels of the indicators of risk, or "biomarkers," known as highly sensitive troponin T (cTnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP).
Higher levels of either may indicate a degree of sustained heart injury that might not be recognized by outwardly visible symptoms, but which could elevate the risk for congestive heart failure, in which the heart has difficulty pumping enough blood throughout the body.
"Two years ago, we published a study that had looked at this very highly sensitive test that was able to detect small amounts of heart injury in older adults who appeared to be in a normal state of health," said deFilippi, an associate professor of medicine in the university's division of cardiology.
Along with other signs, the researchers found that detectable levels of a specific biomarker "was associated with a higher risk of dying years later from cardiovascular disease, particularly if these levels notably changed in a short period of time."
The latest study explored ways of reducing that risk through lifestyle changes.
"We found that there is a very powerful association with physical activity among older adults, so that those who are the most active are one-third as likely to have this marker for heart injury rise over the years, compared with those who are the most sedentary," deFilippi said.
"This relationship between exercise and protection against heart injury was quite dramatic," he added. "We were surprised at the extent of the association. And we also found that the benefit really starts right away."
The new findings were published in the Nov. 14 online issue of the Journal of the American College of Cardiology.
The authors tracked cTnT and NT-proBNP levels for two to three years among a group of more than 2,900 American adults aged 65 and older, drawn from a larger study on cardiovascular health.
Study participants were asked to report on their routine physical activity patterns. The probability that levels of either cTnT or NT-proBNP would rise over the study period was found to go down as exercise went up.
What's more, the research team found that the higher an individual's activity score, the lower their long-term risk for heart failure.
The authors concluded that moderate physical activity does indeed appear to lower the risk for experiencing both cardiac injury and, ultimately, heart failure.
Commenting on the study findings, Mona Fiuzat, an assistant professor in medicine in the departments of medicine and medicine-clinical pharmacology at Duke University, said the study "suggests that exercise may have an important effect on the molecular level to keep the heart healthy." Fiuzat was not involved with the study.
"The clinically important question these authors were trying to answer was whether moderate levels of physical activity can protect elderly people from developing heart failure, which is one of the most common causes of death," Fiuzat said. "And what they found when they followed up on patients two to three years after the study started was that not only did participants with higher levels of physical activity have less of an increase in these [biomarker] proteins, but they had a far lower risk of developing heart failure," she added.
"This," Fiuzat said, "is an excellent first step towards answering some key unanswered questions: What is the mechanism by which exercise helps the heart in patients with heart disease? Can we tailor patient-specific recommendations for intensity and frequency of exercise? Could your doctor one day use blood tests to prescribe and measure benefits of exercise, the same way we treat cholesterol levels today?"
While the study found an association between physical activity among older adults and reduced risk of heart injury, it did not prove a cause-and-effect relationship.
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