VO2 Max: The Single Best Predictor of How Long You'll Live

VO2 max measures how much oxygen your body can use during maximal exertion, and it has become one of the most consistently strong predictors of all-cause mortality in large cohort studies. Research following hundreds of thousands of patients over decades has repeatedly found that moving from the lowest fitness category to even just below-average fitness is associated with a substantial drop in death risk, larger than the reductions typically linked to quitting smoking or controlling blood pressure.

The relationship is dose-dependent and appears to have no upper ceiling in the data collected so far. People in the highest fitness percentile show markedly lower mortality than those in the next bracket down, which is unusual for a health metric. Most people never get VO2 max directly tested, since it typically requires a supervised treadmill test with gas analysis, though several wearables now offer rougher estimates based on heart rate and pace.

Why this matters for tracking: tracking cardiorespiratory fitness, even through an estimate, gives you a single number that correlates with long-term survival more strongly than most bloodwork most people obsess over.