Change in Submaximal Cardiorespiratory Fitness and All-Cause Mortality

To evaluate the relationship between change in submaximal cardiorespiratory fitness (sCRF) and all-cause mortality risk in adult men and women.

A prospective study with at least 2 clinical visits (mean follow-up time, 4.2±3.0 years) between April 1974 and January 2002 was conducted to assess the relationship between change in sCRF and mortality risk during follow-up. Participants were 6106 men and women. Submaximal CRF was determined using the heart rate obtained at the 5-minute mark of a graded maximal treadmill test used to determine maximal CRF (mCRF). Change in sCRF from baseline to follow-up was categorized into 3 groups: increased fitness (decreased heart rate, <-4.0 beats/min), stable fitness (heart rate, -4.0 to 3.0 beats/min), and decreased fitness (increased heart rate, >3.0 beats/min).

The mean change in sCRF at follow-up for all 6106 study participants was -0.5±10.0 beats/min, and the mean change in mCRF was -0.3±1.4 metabolic equivalents. Change in sCRF was related to change in mCRF, though the variance explained was small (R²=0.21; P<.001). The hazard ratios (95% CIs) for all-cause mortality were 0.60 (0.38-0.96) for stable and 0.59 (0.35-1.00) for increased sCRF compared with decreased sCRF after adjusting for age, change in weight, and other common risk factors for premature mortality. The hazard ratios for changes in sCRF and mCRF were not significant after adjusting for changes in mCRF (P=.29) and sCRF (P=.60), respectively.

A simple 5-minute submaximal test of CRF identified that adults who maintained or improved sCRF were less likely to die from all causes during follow-up than were adults whose sCRF decreased.