For people over age 70, starting a twice-weekly walking program didn't lower the odds of heart attack or stroke over the next two years in a U.S. study.

"We had hoped to see a trend for reduced heart disease events, given the strong positive finding for reduced mobility disability, previously published in JAMA," said lead author Dr. Anne B. Newman, director of the University of Pittsburgh Center for Aging and Population Health.

But in this study there was no difference between doing the physical activity and just receiving health education, Newman told Reuters Health by email.

The researchers randomly assigned 1,600 people aged 70 to 89 years who were able to walk at least 400 meters to either a physical activity program or a "successful aging" educational program. Those in the physical activity group aimed for 150 minutes of walking each week plus strength, flexibility and balance training, with two health center visits per week.

Those in the successful aging group attended weekly workshops for the first 26 weeks and monthly sessions thereafter, but there was no exercise component.

Participants self-reported any history of heart attack, heart failure or stroke, and had health assessment clinic visits every six months for an average of about two and a half years.

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During that time, 121 of the 818 physical activity participants suffered a cardiovascular event like heart attack or stroke, as did 113 of the 817 successful aging participants, according to the results in JAMA Cardiology.

"The lack of a difference could mean that physical activity needs to start earlier in life to prevent cardiovascular disease or it could mean that more exercise is needed than what we provided in this study," Newman said. "It is important to recognize that these were frail older adults at high risk for disability."

This level of activity can improve mobility, as found in a previous study, she noted.

"The major benefit of a walking program for people over 70 is in reducing disability and improving mobility," she said.

Muscles can respond to exercise in people well past 90 years of age, so it is never too late to start improving function, she said.

"The benefits probably do not diminish, but the ability to exercise starts to decline in most people in their 40's," as the rate of injury increases, Newman said. "Our program was safe and effective for preventing mobility disability, and was well tolerated by frail older adults over age 70 for an average of two and a half years."

"Studies of cardiac rehab do show that recurrent heart attacks are prevented with exercise," she said.

Not smoking and following a healthy diet can also reduce cardiovascular risk, she said.