Sex-Specific Maximum Predicted Heart Rate and Its Prognosis for Mortality and Myocardial Infarction

Abstract

Maximum predicted heart rate (MPHR) is traditionally calculated by (220 - age). However, this formula's validity has been questioned in women. The purpose of this study was to derive sex-specific formulas for MPHR in a clinical population and compare their prognostic significance with the traditional formula. This was a retrospective cohort of adults referred for exercise treadmill testing between 1991 and 2009. Peak heart rate versus age was plotted by sex, and linear regression analysis was used to derive sex-specific MPHR formulas. Cox models were used to calculate risk of death and myocardial infarction (MI) based on attainment of 85% MPHR using both formulas. Of 31,090 patients (mean ± SD, age = 55 ± 10 yr), there were 2824 deaths over 11 ± 5 yr. MPHR was best estimated by 197 - 0.8 × age for women and 204 - 0.9 × age for men (P interaction < 0.001). Compared with the sex-specific formulas, the traditional formula overestimated peak heart rate by 12 ± 2 bpm in women and 11 ± 1 bpm in men. There were 1868 patients (6%) who achieved the target heart rate using the sex-specific formulas but not with the traditional formula. Achievement of ≥85% MPHR was similarly associated with lower risk of death (adjusted hazard ratio = 0.76 [95% confidence interval = 0.60-0.97] vs 0.75 [0.62-0.90]) and MI (0.71 [0.47-1.06] vs 0.79 [0.57-1.10]) for the sex-specific versus traditional formula. In patients referred for exercise treadmill testing, sex-specific formulas more accurately estimated peak heart rate than the traditional MPHR formula, reclassified 6% of stress tests from inadequate to adequate, and were similarly associated with risk of MI and death.