Improved Reclassification of Mortality Risk by Assessment of Physical Activity in Patients Referred for Exercise Testing

BACKGROUND: Inability to meet minimal guidelines on physical activity is associated with poor health outcomes, but quantifying activity can be complex. We studied whether a simple question regarding participation in regular activity improves risk classification for all-cause mortality. METHODS: Maximal exercise testing was performed in 6962 patients (mean age, 58.9 +/- 11 years) for clinical reasons. Subjects also were assessed for participation in regular activity using a simple yes/no response to meeting minimal recommendations on activity. The incremental value of adding a simple physical activity assessment to clinical, demographic, and exercise test information to predict mortality was determined using Cox proportional hazards models, net reclassification improvement, and integrated discrimination index during a mean follow-up of 9.7 +/- 4 years. RESULTS: Subjects who did not meet the minimal guidelines on activity had a lower exercise capacity (7.4 +/- 4.3 vs 9.1 +/- 3.6 metabolic equivalents, P < .0001) and a higher annual mortality rate (2.42% vs 1.71%, P < .001). Not meeting activity guidelines was associated with an age-adjusted 36% higher risk of mortality (hazard ratio, 1.36; 95% confidence interval, 1.22-1.51, P < .0001). Among clinical and exercise test variables, fitness had the highest C-index for predicting mortality (0.72, P < .001). The addition of physical activity classification to a model including traditional risk factors resulted in a net reclassification improvement of 22.8% (P < .001); adding fitness to the traditional risk factor model resulted in a net reclassification improvement of 43.5% (P < .001). CONCLUSIONS: The addition of a simple assessment of physical activity status significantly improves reclassification of risk for all-cause mortality among patients who are referred for exercise testing. Published by Elsevier Inc.