Exercise keeps high pulse in check

A speedy ticker could increase your chances of suffering a fatal heart attack, according to a new study. But in women, regular workouts might help keep the risk low.

Based on more than 50 000 healthy adults, researchers from Norway found that with each increase of 10 beats per minute in resting heart rate, a woman's risk of dying from a heart attack climbed by 18 % up to the age of 70 years.  For men, the risk rose by 10%. 

High heart rate dangers often overlooked

A healthy heart beats about 60 to 70 times a minute, with some normal variation on either side. If the rate exceeds 80 for an extended period, doctors start to worry -- that is, if they notice, because an elevated pulse may go undetected in otherwise healthy people, said Javaid Nauman of the Norwegian University of Science and Technology in Trondheim, who was involved in the new study.

In the US, heart disease is the leading killer of both men and women. Each year around 1.2 million people suffer a heart attack, and more than one-third die as a result.

High blood pressure, high cholesterol levels and diabetes are well-known risk factors for heart disease, but so far heart rate has been overlooked, experts say.

"It's important to draw attention to heart rate as a cause of heart attack," University of Western Ontario cardiologist Dr Malcolm Arnold said.

He was not involved in the new study, but said its large number of participants made it stand out. According to Nauman and colleagues, their study, published in the Journal of Epidemiology and Community Health, is the first to examine the combined effect of pulse and exercise on fatal heart attacks.

How the study was done

For the analysis, they tapped into data from a large population study in central Norway, selecting only people who did not have known heart disease.

At the outset of the study in 1984 to 1986, the participants filled out questionnaires about their lifestyle and general health, and scientists measured their heart rates and a few other physiological parameters. When the study ended in 2004, more than 10 000 of the participants had died, some 40% due to heart disease.

Overall, men who had a resting heart rate above 100 beats per minute were 73% more likely to die from heart attack than men whose heart rate lay within the healthy range.

For women whose with resting heart rate was above 100 beats per minute, the risk of a fatal heart attack increased by 42% as a whole, and in those younger than 70 years, it more than doubled.

More active you are, less heart disease risk

People who exercised, however, had a considerably lower resting heart rate than those who were more sedentary.

In women, those who reported higher levels of physical activity had a lower risk of dying from heart disease, irrespective of their resting heart rate.

Among the most active, even a heart rate above 87 beats per minute did not lead to a significant increase in heart attacks.

"The most promising thing that we find is that you can keep a check on your resting heart rate by engaging in physical activity," said Nauman, an exercise physiologist, noting that this will reduce the risk of heart attack.

To his knowledge, he added, medications normally used to treat elevated heart rate, such as beta-blockers, have not been shown to have beneficial effects in otherwise healthy people.

People who exercise usually eat healthier

According to Nauman, who is working toward his doctoral degree, the lower heart rate in active people was likely due to exercise's balancing effects on the autonomic nervous system, which can crank our heart beat up and down.

The heart's pace again may influence our cardiovascular health both directly and indirectly. Arnold cautioned that because of the study's design, it is impossible to tease out exactly why active women have a lower risk of heart attack.

For instance, people who exercise often may also have a healthier diet, he said, which has a powerful influence on the heart. Still, he added, the report "confirms the potential benefit of physical activity as part of a healthy life style."  - (Reuters Health, January 2010)