Imboden MT; Harber MP; Whaley MH; Finch WH; Bishop DL; Fleenor BS;
Kaminsky LA.

Progress in Cardiovascular Diseases. 62(2):157-162, 2019 Mar – Apr.

BACKGROUND: The relationship between cardiorespiratory fitness (CRF) and
mortality risk has typically been assessed using a single measurement,
though some evidence suggests the change in CRF over time influences risk.
This evidence is predominantly based on studies using estimated CRF
(CRFe). The strength of this relationship using change in directly
measured CRF over time in apparently healthy men and women is not well
understood.
PURPOSE: To examine the association of change in CRF over time, measured
using cardiopulmonary exercise testing (CPX), with all-cause and
disease-specific mortality and to compare baseline and subsequent CRF
measurements as predictors of all-cause mortality.
METHODS: Participants included 833 apparently healthy men and women
(42.9+/-10.8years) who underwent two maximal CPXs, the second CPX being
>=1year following the baseline assessment (mean 8.6years, range 1.0 to
40.3years). Participants were followed for up to 17.7 (SD 11.8)years for
all-cause-, cardiovascular disease- (CVD), and cancer mortality.
Cox-proportional hazard models were performed to determine the association
between the change in CRF, computed as visit 1 (CPX1) peak oxygen
consumption (VO2peak [mL.kg-1.min-1]) – visit 2 (CPX2) VO2peak, and
mortality outcomes. A Wald-Chi square test of equality was used to compare
the strength of CPX1 to CPX2 VO2peak in predicting mortality.
RESULTS: During follow-up, 172 participants died. Overall, the change in
CPX-CRF was inversely related to all-cause, CVD, and cancer mortality
(p<0.05). Each 1mL.kg-1.min-1 increase was associated with a ~11, 15, and
16% (all p<0.001) reduction in all-cause, CVD, and cancer mortality,
respectively. The inverse relationship between CRF and all-cause mortality
was significant (p<0.05) when men and women were examined independently,
after adjusting for years since first CPX, baseline VO2peak, and age.
Further, the Wald Chi-square test of equality found CPX2 VO2peak to be a
significantly stronger predictor of all-cause mortality than CPX1 VO2peak
(p<0.05).
CONCLUSION: The change in CRF over time was inversely related to
mortality outcomes, and mortality was better predicted by CRF measured at
subsequent test than CPX1 CRF. These findings emphasize the importance of
adopting lifestyle behaviors that promote CRF, as well as support the need
for routine assessment of CRF in clinical practice to better assess risk.