Poor fitness increases risk of death in women more than in men.

Findings from the St. James Women Take Heart Project (WTH) could impact how doctors test and treat women who have no outward signs of heart disease. Researchers, who started the study in 1992 and followed 5,721 Chicago women said physical fitness was a stronger predictor of death than other measures, such as the Framingham Risk Score (a questionnaire based on cholesterol, age blood pressure, diabetes and smoking). A score is totaled and helps physicians decide whether a person is at high risk for dying from heart disease and requires treatment.

"Heart and blood vessel disease is the No. 1 killer of both men and women. Earlier studies showed an association between poor exercise capacity and poor survival in men with or without heart disease, but this is the first study large enough to examine the issue in a cross-section of healthy women," said Martha Gulati, M.D., M.S., an assistant professor of medicine and preventive medicine at Rush Presbyterian St. Luke's Medical Center in Chicago.

The average age of the women was 52. None of them had heart disease; many had high blood pressure, high cholesterol, diabetes or other risk factors. At the study's start, each woman had an exercise stress test on a treadmill that became steeper and faster every three minutes until she became breathless, dizzy or exhausted.

Researchers measured fitness level, also called exercise capacity, in metabolic equivalents (MET). Fitness levels ranged from 1.5 MET for those with the lowest exercise capacity to 20 METs for the most physically fit women. The average fitness level was 8 METs. Researchers compared women's exercise capacity to death from all causes during the next eight years.

"For every 1-MET increase in exercise capacity, there was a 17 percent decrease in the risk of death," Gulati said.

A similar study on men without heart disease conducted at the Cooper Aerobics Center/Cooper Clinic in Dallas found a 7.9 percent decrease in death in men for every one minute increase in exercise time, an amount of exertion that is nearly equivalent to 1 MET. The average MET score for those who survived was 8.0, compared to 6.2 for those who died.

During the follow-up period, 180 people (3.2 percent) died.

The risk of death doubled for those in the 5- to 8-MET exercise capacity category compared to those above 8 METs.

"Currently, no one recommends routine exercise testing in healthy individuals. Our study has demonstrated a clear clinical rationale for routine stress testing in asymptomatic women. Furthermore, the achieved exercise capacity should be interpreted and translated to the patients to provide important prognostic information. This is one of the most important public health issues, and we've got to start attacking it," Gulati said.

In an accompanying editorial, Daniel 13. Mark, M.D., M.P.H., and Michael S. Lauer, M.D., of the Duke Clinical Research Institute in Durham, N.C., wrote that Gulati's study "provides the most unambiguous evidence to date of its (exercise's) independent prognostic importance."

However, they stop short of recommending exercise testing for asymptomatic patients. This and similar studies clearly imply that improving exercise capacity will improve prognosis, but that hypothesis has not been adequately tested.

"To assess whether modifying exercise capacity alters survival, we need randomized trial data," they said.

They stressed that "great benefits" could result, if the findings showed that physicians could target the most unfit members of our society "before they develop chronic disease."

Information for this article was provided by the American Heart Association.