People with high HRV live longer

HRV declines with age[1]RMSSD by age and gender. When looking at the statistics it appears that the rate of declines slows as we get older, and then reverses after 80[2]Relation of high heart rate variability to healthy longevity. The reason for this pattern lies in the way that averages work. 

People with lower HRV die sooner, dropping out of the population. Losing the people with lower HRV results in a slowing of the decline in the averages, and ultimately a reversal, as only the people with the highest HRV continue to live on.

Improving HRV is a choice, based on lifestyle. Read: Improving the numbers