Nomogram Evaluating Exercise Capacity Can Predict Survival in Women

Exercise capacity is an independent predictor of mortality in women, results from a study of 5,721 asymptomatic women.

“Recent studies have demonstrated that exercise capacity is an independent predictor of mortality in women,” write Martha Gulati, MD, from Rush University Medical Center in Chicago, Illinois, and colleagues. “Normative values of exercise capacity for age in women have not been well established.”

In this study, 5,721 asymptomatic women underwent a symptom-limited maximal stress test, with exercise capacity measured in metabolic equivalents (METs). Linear regression analysis estimated the mean MET achieved for age and a nomogram to estimate the percentage of predicted exercise capacity on the basis of age and the exercise capacity achieved. This nomogram determined the percentage of predicted exercise capacity in the original cohort and in a referral population of 4,471 women with cardiovascular symptoms who also underwent symptom-limited stress testing. All-cause and cardiac mortality were estimated using Cox survival analysis.

In the cohort of asymptomatic women, the nomogram for predicted exercise capacity in METs on the basis of age was as follows: predicted MET = 14.7 – (0.13 × age). In asymptomatic women with an exercise capacity of less than 85% of the predicted value for age, the risk of death was twice that of women with an exercise capacity of at least 85% of the age-predicted value (P < .001).

The cohort of symptomatic women had similar findings. At all ages, more physically active women had a greater exercise capacity. In the asymptomatic women, sensitivity for predicting the risk of death from any cause was 70% and specificity was 47%.

“We have established a nomogram for predicted exercise capacity on the basis of age that is predictive of survival among both asymptomatic and symptomatic women,” the authors write. “These findings could be incorporated into the interpretation of exercise stress tests, providing additional prognostic information for risk stratification.”

The primary study limitation was that the nomogram was created from data on a volunteer cohort of asymptomatic, mostly white women, and the referral population differed from the asymptomatic cohort.

“By confirming the critical importance of fitness to health and longevity, the authors place a responsibility on clinicians to use this information for their patients’ benefit,” Drs. Kraus and Douglas write. “Given that such data are readily obtainable in the clinical setting (and often ignored when available on routine exercise testing), compliance should be fairly easy and inexpensive and represents an effective improvement in practice. We hope that this report will provide a stimulus to reintroduce fitness assessments into the routine clinical environment for both women and men.”

Study keynotes: Exercise capacity decreases with increasing age, with lower exercise capacity for sedentary vs active women for all ages. And A nomogram for exercise capacity specific to women, using a cutoff of 85% of predicted capacity, is predictive of overall and cardiac mortality in both asymptomatic and symptomatic women.
N Engl J Med. 2005;353:468-475, 517-519