Does running add years to your life?

With the Oklahoma City Memorial Marathon just around the corner, I have running on my mind.

According to a story I read, every hour you spend running adds seven hours to your life. That sounds like a pretty good return on investment. But does that really hold true? And what about all the bad press I’ve heard about how running may be bad for the heart?

The story you read most likely referred to a study that appeared earlier this month in the scientific journal Progress in Cardiovascular Disease.

In it, scientists analyzed data gathered from more than 50,000 patients who’d visited the Cooper Clinic in Texas between 1971 and 2002.They found that the most powerful prevention of premature death — even more powerful than quitting smoking, reducing blood pressure or reaching a healthy body mass index — was running. The researchers determined that if all 40,000 or so non-runners who had been part of the study had taken up running, there would have been 16 percent fewer deaths overall.

The scientists also calculated that for the average runner, running returns more to people’s lives than it takes. They calculated that a typical runner would spend less than six months running over the course of 40 years, but with these kinds of exercise levels (roughly two hours a week), you’d expect an increase in life expectancy of 3.2 years. In other words, for every hour you hit the roads, you’d expect to live an additional six to seven hours. Obviously, these gains aren’t infinite. The researchers found that they topped out at about three years. So this study doesn’t suggest you’ll live to be 107.

Interestingly, though, it doesn’t suggest you won’t live to107. Based on past studies, some researchers had hypothesized that running “to excess” might cause damage to the heart that would actually lead to shortened lives. This study found no evidence of that.

So, while putting in 40, 50 or more miles per week may not net you any additional gains in life span, it doesn’t appear to lead to an increased risk of heart disease or cardiac events.

The researchers found that the life span gains came even if people started running later in life. They also determined that as little as five minutes of running each day was linked to added life spans. When compared to other activities such as walking or biking, running showed the most profound gains.

This was an epidemiological study, meaning it just looked for associations among a population of participants. That means it can’t tell us why running seems to serve as a more powerful life extender than other forms of physical activities. But a recent study from the Mayo Clinic offers a clue.

There, scientists looked at the cellular impact of exercise on the muscles of people of differing ages. They found that among various forms of exercise, interval training was universally most effective at improving the health of their mitochondria, the energy-producing “engine” of cells. Indeed, in some ways, older people’s cells responded in a more pronounced fashion to the intense workouts.

Running is a quick and efficient way to get a workout that’s more intense than walking — and usually also more intense than biking. This intensity may be key to why it’s so effective at lengthening lives. To answer this question more definitively, we need further studies.

Still, the good news is obvious: These studies offer further proof of the benefits of running and intense exercise. While running certainly won’t make you invincible, so long as you pay attention to any warning signs your body might send, you can hit the road all you want.

That, of course, includes the Oklahoma City Memorial Marathon. Come April 30, I will support this great event in my customary fashion: sitting in the driveway with a coffee and the paper, cheering on all you healthy folks!