Keeping physically fit dramatically protects women against the ravages of heart disease, which kills 255,000 women each year, according to a landmark study released Tuesday.
Chicago researchers who tracked more than 5,700 women for eight years discovered that the least fit were three times more likely to die of coronary artery disease during that period than women at peak physical capacity.
"You can be completely healthy, have no cardiac risk factors, but if you're not able to achieve a good exercise capacity or physical fitness . . . you're at high risk of dying," said Dr. Martha Gulati, lead author of the study and a cardiologist at Rush University Medical Center. "Exercise is good and physical fitness is really important, and maybe more important in women than in men."
The finding, which appears in the journal Circulation, is being published four months after health authorities warned that 46 million more Americans are at substantial risk of developing hypertension than previously believed. It also provides further ammunition for public health authorities sounding an alarm about heart disease, the leading killer of women, but one that is often silent.
Still, specialists said Monday that they remain pessimistic about the prospect of altering behavior.
"The societal forces against us are huge," said Dr. Ira Ockene, director of the preventive cardiology program at the University of Massachusetts Medical School in Worcester. "Everything is designed to make it more difficult for us to be physically active and easier to sit, and that is really problematic."
The study, a milestone in research into coronary artery disease, is believed to be the first large-scale report on the link between physical fitness and heart ailments in women.
Even though women account for 49 percent of all heart-disease deaths, they have often been neglected in research and even treatment, a legacy both of gender bias and the fact that cardiac conditions manifest themselves in women later than in men, which some scientists speculate has made women less-prime candidates for study.
"This is a very important study for women," said Dr. Paula Johnson, executive director of the Connors Center for Women's Health and Gender Biology at Brigham and Women's Hospital. "It should hopefully spur research in an area that does not receive as much attention, which is how do you actually improve levels of physical fitness."
For the new study, the researchers gauged the women's ability to exercise using a stress test. Each woman stepped onto a treadmill, which grew faster and steeper every three minutes.
From 1992 to 2000, the women — who had no symptoms of heart disease at the start of the study — were followed by researchers. They found that the least physically fit were more likely to die, even after taking into account traditional sources of coronary ailments such as high cholesterol and elevated blood pressure.
In fact, the Chicago researchers compared their findings in women with earlier studies examining men and discovered that lack of fitness was even more dangerous for women than men. A one unit increase in exercise capacity resulted in a 17 percent decrease in chances a woman would die, compared with just 12 percent in men, the researchers found.
Cardiologists said Monday that it is still too soon to recommend that every woman should routinely be subjected to a stress test, in part because of the cost of such exams. Instead, they recommended that physicians use other measurements of fitness, including questionnaires.
But the study will help physicians have frank discussions about life expectancy with women who have the tests.
"If a woman only goes for a short duration on the stress test, it tells a lot about what their future holds for them," Gulati said.
Independent scientists said more research will be needed to prove conclusively that more exercise leads to a longer life. But cardiologists recommended that the findings on the link between fitness levels and heart disease be used to encourage patients to pursue healthier lives.
"We can approach every patient who comes into the office and say, 'We know now that the more fit you are, the less likely you are to die in the next 10 years,' " said Dr. Gary J. Balady, a cardiologist at the Boston University School of Medicine.