Over 150 minutes of moderate to vigorous activity each week, such as brisk walking or biking, in middle age may significantly decrease the risk of heart failure, according to a study. By analysing reported physical activity levels over time in 11,000 American adults, researchers at Johns Hopkins University in the US found that increasing physical activity to recommended levels over as few as six years in middle age is associated with a lower risk of heart failure. The analysis, published in the journal Circulation, also found that as little as six years without physical activity in middle age was linked to an increased risk of the disorder. Unlike heart attack, in which heart muscle dies, heart failure is marked by a long-term, chronic inability of the heart to pump enough blood, or pump it hard enough, to bring needed oxygen to the body. "Our findings suggest that consistently participating in the recommended 150 minutes of moderate to vigorous activity each week, such as brisk walking or biking, in middle age may be enough to reduce your heart failure risk by 31 per cent," said Chiadi Ndumele, an assistant professor at the Johns Hopkins University School of Medicine. "Additionally, going from no exercise to recommended activity levels over six years in middle age may reduce heart failure risk by 23 per cent," said Ndumele. The researchers caution that their study was observational, meaning the results do not show a direct cause-and-effect link between exercise and heart failure. However, they say the trends observed in data gathered on middle-aged adults suggest that it may never be too late to reduce the risk of heart failure with moderate exercise. "The population of people with heart failure is growing because people are living longer and surviving heart attacks and other forms of heart disease," said Roberta Florido, a cardiology fellow at the Johns Hopkin. "Unlike other heart disease risk factors like high blood pressure or high cholesterol, we don't have specifically effective drugs to prevent heart failure, so we need to identify and verify effective strategies for prevention and emphasize these to the public," said Florido. The researchers used data already gathered from 11,351 participants in the long term Atherosclerosis Risk in Communities (ARIC) study. The participants' average age was 60, 57 per cent were women and most were either white or African-American. Participants were monitored annually for an average of 19 years for cardiovascular disease events such as heart attack, stroke and heart failure using telephone interviews, hospital records and death certificates. Over the course of the study there were 1,693 hospitalisations and 57 deaths due to heart failure. The "recommended" amount is at least 75 minutes per week of vigorous intensity or at least 150 minutes per week of moderate intensity exercise. Those with recommended activity levels showed the highest associated heart failure risk decrease, at 31 per cent compared with those with consistently poor activity levels.