Many people adhere to the American Heart Association’s recommendation to exercise 30 minutes a day.

But is that enough to prevent heart failure? A new study indicates that it’s not.

Heart failure refers to the condition in which a person’s heart becomes so weak that it can no longer pump blood to the rest of the body.

Nearly 5 million Americans are living with heart failure, and approximately 550,000 people are diagnosed with the problem each year.

This condition results in a significant number of deaths, and given the aging population, is expected to increase markedly in the coming years, the American Heart Association says.

A research team at the University of Texas Southwestern Medical School reviewed 12 studies that looked at nearly 370,500 men and women who self-reported their levels of physical activity.

Over a follow-up time of 15 years, the group experienced 20,203 heart failure events.

Those people that followed the AHA’s “30-minutes-a-day” guidelines for exercise showed “modest reductions” in heart failure risk. On the other hand, those who exercised 2 to 4 times as much reduced their risk a “substantial” 20 to 35 percent, the researchers said.

The researchers also found that physical activity and heart failure may be “dose dependent,” meaning that higher levels of physical activity appeared to be linked to a lower risk of heart failure.

That association appeared to hold across age groups, gender, and race.

I’ve long thought that 30 minutes of exercise is not enough. That’s why I recommend a one-hour daily walk to my patients. This is a goal that can be worked up to gradually.