Figure 2. Comparison of the relationship of low frequency heart rate variability and vital exhaustion quartile by heart rate variability‐age units.

Heart rate variability‐age units were calculated by the ratio of the coefficient for vital exhaustion by the coefficient for age in models predicting low frequency heart rate variability. The effect of having the highest quartile of exhaustion was equivalent to an increase of ≈ 4 years of heart rate variability‐age (as measured by low frequency heart rate variability). HRV indicates heart rate variability, and LF, low frequency.