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To predict your longevity, you have two main options. You can rely on the routine tests and measurements your doctor likes to order for you, such as blood pressure, cholesterol levels, weight, and so on. Or you can go down a biohacking rabbit hole the way tech millionaire turned did to live longer. Johnson’s obsessive self-measurement protocol involves tracking more than a hundred biomarkers, ranging from the telomere length in blood cells to the speed of his urine stream (which, at 25 milliliters per second, he reports, is in the 90th percentile of 40-year-olds).

Or perhaps there is a simpler option. The goal of self-measurement is to scrutinize which factors truly predict longevity, so that you can try to change them before it’s too late. A new study from biostatisticians at the University of Colorado, Johns Hopkins University, and several other institutions crunched data from the long-running National Health and Nutrition Examination Survey (NHANES), comparing the predictive power of 15 potential longevity markers. The winner—a better predictor than having diabetes or heart disease, receiving a cancer diagnosis, or even how old you are—was the amount of physical activity you perform in a typical day, as measured by a wrist tracker. Forget pee speed. The message to remember is: move or die.

How to Live Longer

It’s hardly revolutionary to suggest that exercise is good for you, of course. But the fact that people continue to latch on to ever more esoteric minutiae suggests that we continue to undersell its benefits. That might be a data problem, at least in part. It’s famously hard to quantify how much you move in a given day, and early epidemiological studies tended to rely on surveys in which people were asked to estimate how much they exercised. Later studies used cumbersome hip-mounted accelerometers that were seldom worn around the clock. The , published in Medicine and Science in Sports and Exercise, draws on NHANES data from subjects recruited between 2011 and 2014, the first wave of the study to employ convenient wrist-worn accelerometers that stay on all day and night.

Sure enough, it turns out that better data yields better predictions. The study zeroed in on 3,600 subjects between the ages of 50 and 80, and tracked them to see who died in the years following their baseline measurements. In addition to physical activity, the subjects were assessed for 14 of the best-known traditional risk factors for mortality: basic demographic information (age, gender, body mass index, race or ethnicity, educational level), lifestyle habits (alcohol consumption, smoking), preexisting medical conditions (diabetes, heart disease, congestive heart failure, stroke, cancer, mobility problems), and self-reported overall health. The best predictors for how to live longer? Physical activity, followed by age, mobility problems, self-assessed health, diabetes, and smoking. Take a moment to let that sink in: how much and how vigorously you move are more important than how old you are as a predictor of the years you’ve got left.

These results don’t arrive out of nowhere. Back in 2016, the American Heart Association issued a scientific statement calling for cardiorespiratory fitness, which is what VO2 max tests measure, to be considered a vital sign that doctors assess during routine checkups. The accumulated evidence, according to the AHA, indicates that low VO2 max is a potentially stronger predictor of mortality than usual suspects like smoking, cholesterol, and high blood pressure. But there’s a key difference between the two data points: VO2 max is about 50 percent determined by your genes, whereas how much you move is more or less up to you.

Fitness Trackers Are Key to New Longevity Findings

All this suggests that the hype about wearable fitness trackers over the past decade or so might be justified. Wrist-worn accelerometers like Apple Watches, Fitbits, and Whoop bands, according to the new data, are tracking the single most powerful predictor of your future health. There’s a caveat, though, according to Erjia Cui, a University of Minnesota biostatistics professor and the joint lead author of the study. Consumer wearables generally spit out some sort of proprietary activity score instead of providing raw data, so it isn’t clear whether those activity scores have the same predictive value as Cui’s analysis. Still, the results suggest that tracking your total movement throughout the day, rather than just formal workouts, might be a powerful health check.

The inevitable question, then, is how much movement, and of what type, we need in order to live longer. What’s the target we should be aiming for? Cui and his colleagues track the raw acceleration data in increments of a hundredth of a second, which doesn’t translate very well to the screen of your smartwatch. The challenge remains about how to translate that flood of data into simple advice regarding how many minutes of daily exercise you need, how hard that exercise needs to be, and how much you should move around when not exercising.

To be honest, though, I’m not sure the quest to determine an exact formula for how much we should move is all that different from the belief that measuring your urine speed will give you actionable insights about your rate of aging. Metrics do matter, and keeping tabs on biomarkers backed by actual science, like blood pressure, makes sense. But it’s worth remembering that the measurement is not the object; the map is not the road. What’s exciting about Cui’s data is how it reshuffles our priorities, shifting the focus from all the little things our wearable tech now tracks to the one big thing that really works—and which is also a worthwhile goal for its own sake. Want to live longer? Open the door, step outside, and get moving.