Original article
Change in Maximal Exercise Capacity Is Associated With Survival in Men and Women

https://doi.org/10.1016/j.mayocp.2016.12.016Get rights and content

Abstract

Objective

To describe the relationship between change in maximal exercise capacity (MEC) over time and risk of all-cause mortality separately in men and women.

Patients and Methods

Consecutive patients (n=10,854; mean ± SD age, 54±11 years; 43% women; 30% nonwhite) who completed 2 physician-referred exercise tests between January 2, 1991, and May 28, 2009, were identified from the Henry Ford Exercise Testing (FIT) Project. The MEC was quantified in metabolic equivalents of task (METs) calculated from peak workload on a treadmill and adjusted to the equivalent for a 50-year-old man. Multivariable Cox proportional hazards regression was performed to assess risk of all-cause mortality associated with change in MEC based on (1) change from age-/sex-adjusted low fitness (<8 METs) to intermediate or high fitness and (2) an absolute change in METs.

Results

Relative to patients with low fitness at both tests, increasing from low to intermediate or high fitness was associated with lower risk of all-cause mortality (adjusted hazard ratio [aHR] = 0.63 [95% CI, 0.45-0.87] in men and 0.56 [95% CI, 0.34-0.91] in women). Each 1-MET increase in age-/sex-adjusted MEC between baseline and follow-up was associated with an aHR of 0.87 (95% CI, 0.84-0.91) in men and 0.84 (95% CI, 0.79-0.89) in women, with no significant interaction by sex (P=.995). Similar aHRs were observed in a subgroup with intermediate fitness at baseline.

Conclusion

In men and women referred for an exercise stress test, change in MEC over time is inversely related to risk of all-cause mortality.

Section snippets

Study Design

The Henry Ford Exercise Testing (FIT) Project is a retrospective observational study based on administrative and electronic medical record data. Design details of the FIT Project have been published previously.17 The FIT Project comprises consecutive patients 18 years and older who performed a physician-referred exercise stress test between January 2, 1991, and May 28, 2009, at Henry Ford Hospital and affiliated medical centers in Detroit, Michigan, and the metropolitan area. In the present

Results

Characteristics of the cohort at baseline are shown in Table 1. Compared with men, a lower percentage of women were of white race, recent tobacco smokers, classified as low fitness, and dyslipidemic at baseline. On average, women had lower METs than men at baseline but higher METs when adjusted to the equivalent for a 50-year-old man. Median time between baseline and follow-up exercise stress tests was 3.8 years (interquartile range [IQR], 2.3-6.2 years) in men and 3.9 years (IQR, 2.3-6.1

Discussion

In both men and women who completed 2 physician-referred exercise stress tests at least 12 months apart, maintaining or improving MEC above an age-/sex-adjusted low fitness category (equivalent to <8 METs for a 50-year-old man) was independently associated with a lower risk for all-cause mortality compared with patients who remained in a low fitness category. Compared with patients with low fitness at both tests, increasing MEC from low to intermediate or high fitness was associated with a 37%

Conclusion

In individuals referred for an exercise stress test, change in MEC over time is inversely related to risk of all-cause mortality. Based on low fitness defined as less than 9 METs and less than 7 METs at age 40 years, less than 8 METs and less than 6 METs at age 50 years, and less than 7 METs and less than 5 METs at age 60 years for men and women, respectively; increasing MEC above low fitness is associated with reduced all-cause mortality risk. These data support the importance of encouraging

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    Potential Competing Interests: Dr Blaha reports receiving grants from Aetna Foundation, the American Heart Association, the National Institutes of Health, and the Food and Drug Administration; and receiving personal fees from and serving on the advisory boards of Novartis, Amgen, Akcea, Luitpold Pharmceuticals, Pozen, and the American College of Cardiology.

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