Oxygen Uptake Efficiency Slope as a Predictor of Mortality Risk: THE BALL STATE ADULT FITNESS LONGITUDINAL LIFESTYLE STUDY (BALL ST).

PURPOSE

Oxygen uptake efficiency slope (OUES), defined as the slope of the linear relationship between oxygen uptake and the semilog transformed ventilation rate measured during an incremental exercise test, may have prognostic utility. The objective of this investigation was to examine the relationship between assessments of OUES and all-cause mortality in a cohort of apparently healthy adults.

METHODS

The sample included 2220 apparently healthy adults (48% females) with a mean age of 44.7 ± 12.9 yr who performed cardiopulmonary exercise testing. The OUES was calculated from the entire test, using data from the initial 50% (OUES 50 ) and 75% (OUES 75 ) of test time, and normalized to body surface area. Cox proportional hazard models assessed the relationship between measures of OUES and mortality. Prognostic peak oxygen uptake (V˙ o2peak ) and OUES models were compared using the concordance index.

RESULTS

There were 310 deaths (29% females) over a follow-up period of 19.8 ± 11.1 yr. For males, OUES, OUES 75 , and normalized OUES had an inverse association with mortality, even after adjusting for traditional risk factors ( P < .05). For females, only the unadjusted OUES, OUES 75 , and normalized OUES models were associated with mortality ( P < .05). The concordance index values indicated that unadjusted OUES 50 and OUES 75 models had lower discrimination than the unadjusted OUES and V˙ o2peak models ( P < .05). Furthermore, OUES did not complement the fully adjusted V˙ o2peak model ( P ≥ .32).

CONCLUSIONS

Assessments of OUES are related to all-cause mortality in males but not in females. These findings suggest that OUES can have prognostic utility in apparently healthy males. Moreover, submaximal determinations of OUES could have value when measuring V˙ o2peak is not feasible.