With heart failure, the cardiac muscle is unable to pump blood at the normal rate, resulting in persistent tiredness, breathlessness, and swollen legs. The condition can appear with age and tends to worsen over time.
The most salient risk factors for this condition, according to the Centers for Disease Control and Prevention (CDC), are: hypertension, a history of coronary heart disease or heart attacks, and diabetes.
Since this condition, once acquired, has to be managed for life, healthcare professionals recommend preventive strategies.
These usually involve making more healthful lifestyle choices by acquiring good dietary habits and exercising regularly.
But how do fluctuations in a person's levels of physical activity influence their risk of experiencing heart failure? That is what Dr. Chiadi Ndumele and colleagues, from Johns Hopkins University in Baltimore, MD, and other institutions set out to clarify.
In a new study — the findings of which have now been published in the journal Circulation — Dr. Ndumele and team investigate whether individuals who are active until middle age, but then become more sedentary, are more exposed to heart failure and vice versa.
"The population of people with heart failure is growing," says first study author Dr. Roberta Florido, "because people are living longer and surviving heart attacks and other forms of heart disease."
"Unlike other heart disease risk factors like high blood pressure or high cholesterol, we don't have specifically effective drugs to prevent heart failure," she notes, "so we need to identify and verify effective strategies for prevention and emphasize these to the public."
It's never too late to exercise more
The research team analyzed data sourced from 11,351 people using the long-term
They were monitored over a period of 19 years, on average, and records were kept about instances of cardiovascular disease events — including heart failure, stroke, and heart attack — on a yearly basis.
Moreover, each participant was asked to delineate their exercise habits on two ARIC study visits — first at baseline, and then again after 6 years. The researchers then used this information to rate everyone's levels of physical activity.
Measuring the study participants' exercise habits against the American Heart Association's (AHA) recommendations, they were categorized as:
- poor, if the individual did not typically exercise
- intermediate, if exercise levels corresponded to those outlined by the AHA — that is, a minimum of 75 minutes of "vigorous" exercise per week, or at least 150 minutes of "moderate" exercise per week
Dr. Ndumele and his collegues noted that the participants that met recommended exercise levels both at baseline and at the 6-year mark appeared to enjoy the greatest benefits to heart health, with a 31 percent lower risk of heart failure, compared with their peers who had poor physical activity habits during the same timeline.
But those participants who increased their levels of physical activity over that 6-year period also experienced benefits. Heart failure risk decreased by 12 percent among individuals who upped their fitness levels from poor to intermediate.
And the reverse was also true — participants who gave up exercise during those 6 years saw an 18 percent increase in heart failure risk.
"In everyday terms," notes Dr. Ndumele, "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 percent."
"Additionally," he says, "going from no exercise to recommended activity levels over 6 years in middle age may reduce heart failure risk by 23 percent."
At what rate must we up our exercise levels?
The research team also wanted to ascertain by how much an individual would need to increase their levels of physical activity in order to lower their risk of experiencing heart failure.
To do so, they calculated physical activity as "metabolic equivalents" (METs) and described one MET as 1 kilocalorie per kilogram per hour, which was equivalent to a passive activity, such as sitting down and watching TV.
Different activities corresponded to different MET levels; for instance, walking fast would be 3 METs, jogging 7 METs, and jumping rope 10 METs.
They determined that every increase of 750 MET minutes per week over a 6-year period would reduce the risk of heart failure by 16 percent. Also, every increase of 1,000 MET minutes per week would result in a 21 percent lower risk of heart failure.
That being said, Dr. Ndumele and his team also warn that their study was observational, and so the relationship between physical activity levels and the decreased risks to heart health should not be automatically taken as causational.
Even so, they note that the trends they observed are consistent enough to indicate that individuals may benefit from adhering to exercise guidelines in middle age.