Heart rate variability in the prediction of mortality: A systematic review and meta-analysis of healthy and patient populations

Researchers combined results from many earlier studies. The studies included healthy people and people with medical conditions. They examined heart rate variability, the small changes in time between heartbeats, and whether it was linked with later death. Overall, lower heart rate variability tended to be linked with a higher risk of death. The studies differed in their participants, measurements, and health conditions, so the results do not prove that low variability causes death.

What this means for you: This suggests heart rate variability may be a useful health warning sign, but it is not a diagnosis or a proven way to extend life. You do not need to buy a wearable just to improve this number, especially because consumer devices may measure it differently.