And a few people questioned whether running really added materially to people’s life spans. Could it be, they asked rather peevishly, that if in order to reduce your risk of dying by a year, you had to spend the equivalent of a year’s worth of time on the trails or track, producing no discernible net gain?
So for the new study, which was published last month in Progress in Cardiovascular Disease, Dr. Lee and his colleagues set out to address those and related issues by reanalyzing data from the Cooper Institute and also examining results from a number of other large-scale recent studies looking into the associations between exercise and mortality.
Over all, this new review reinforced the findings of the earlier research, the scientists determined. Cumulatively, the data indicated that running, whatever someone’s pace or mileage, dropped a person’s risk of premature death by almost 40 percent, a benefit that held true even when the researchers controlled for smoking, drinking and a history of health problems such as hypertension or obesity.
Using those numbers, the scientists then determined that if every nonrunner who had been part of the reviewed studies took up the sport, there would have been 16 percent fewer deaths over all, and 25 percent fewer fatal heart attacks. (One caveat: the participants in those studies were mostly white and middle class.)
Perhaps most interesting, the researchers calculated that, hour for hour, running statistically returns more time to people’s lives than it consumes. Figuring two hours per week of training, since that was the average reported by runners in the Cooper Institute study, the researchers estimated that a typical runner would spend less than six months actually running over the course of almost 40 years, but could expect an increase in life expectancy of 3.2 years, for a net gain of about 2.8 years.
In concrete terms, an hour of running statistically lengthens life expectancy by seven hours, the researchers report.
Of course, these additions “are not infinite,” Dr. Lee says. Running does not make people immortal. The gains in life expectancy are capped at around three extra years, he says, however much people run.
The good news is that prolonged running does not seem to become counterproductive for longevity, he continues, according to the data he and his colleagues reviewed. Improvements in life expectancy generally plateaued at about four hours of running per week, Dr. Lee says. But they did not decline.
Meanwhile, other kinds of exercise also reliably benefited life expectancy, the researchers found, but not to the same degree as running. Walking, cycling and other activities, even if they required the same exertion as running, typically dropped the risk of premature death by about 12 percent. (To make my own biases clear, I run but I also love cycling and I walk my dogs every day.)
Why running should be so uniquely potent against early mortality remains uncertain, Dr. Lee says. But it is likely, he says, that it combats many of the common risk factors for early death, including high blood pressure and extra body fat, especially around the middle.
It also raises aerobic fitness, he says, and high aerobic fitness is one of the best-known indicators of an individual’s long-term health.
Of course, the findings in this new review are associational, meaning that they prove that people who run tend also to be people who live longer, but not that running directly causes the increases in longevity. Runners typically also lead healthy lives, Dr. Lee says, and their lifestyles may be playing an outsize role in mortality.
But even taking that possibility into consideration, he says, the data suggest that running could add years to our lives.
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