The research team, which was led by Ulf Ekelund, PhD, of the Norwegian School of Sports Sciences in Oslo, Norway, searched five medical/science databases. They selected nine applicable studies from four countries (Sweden, Norway, the United Kingdom and the United States) and then conducted what they called a “harmonized meta-analysis.” In these studies, 44,370 men and women were followed for time spans ranging from 4 to 14 ½ years. The subjects’ physical activity was measured by fitness trackers equipped with an accelerometer (most wearable fitness trackers nowadays use accelerometers to track movement in three dimensions while measuring acceleration, frequency, duration and intensity). The time the subjects spent sitting, or sedentary time, was also measured.
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The researchers then divided the subjects into three groups, depending on their level of daily activity and on how many hours a day they spent sitting. They also counted the number of people who died during the study period — 3,451. It came as no surprise that those in the top third for sitting and the bottom third for activity were the most likely to suffer premature death (in fact, they were 260% more likely to die than those who were most active and spent the least amount of time sitting).
However, the researchers did come up with one unanticipated finding. People in the middle third for activity were significantly less likely to die prematurely than those in the group that sat the most, and people who exercised moderately for just 11 minutes a day were classified in the middle third. Not that 11 minutes a day turned out to be an ideal amount of exercise. The researchers calculated that 30 to 40 minutes of daily physical activity was optimal — this had the healthiest effect on longevity, regardless of how long the subjects spent sitting.
The observations in the new report seemed to clash with previous recommendations on daily activity. Earlier guidelines from the World Health Organization stated that all adults should have about 150 to 300 minutes of moderate-intensity physical activity every week, while some studies have indicated that an hour to 75 minutes of exercise was needed every day to extend life spans.
The authors of the new study theorized that the discrepancy might be explained by the fact that earlier studies relied on the subjects’ “self-reporting” of their exercise activity and that people either aren’t that good about remembering how much they exercised or they exaggerate. In an earlier study on exercise, Ekelund explained, “Unfortunately, self-reported physical activity is prone to misreporting because people may often regard their levels of physical activity as higher than they actually are. The unhealthier the population, the more this misreporting tends to happen.” Research based on hard data from fitness trackers gives greater accuracy, and, says Ekelund, according to this research “even doing small amounts of physical activity seemed to be associated with a reduced risk of dying prematurely.” Or as the researchers put it in the new study, “Developing ways to limit sedentary time and increase activity at any level could considerably improve health and reduce mortality.” Walking, they added, might an activity to consider. It’s simple, it’s free, most older adults can accomplish it, and few people have problems that prevent them from walking.
Want to learn more about exercising with diabetes? Read “Add Movement to Your Life,” “Picking the Right Activity to Meet Your Fitness Goals” and “Seven Ways to Have Fun Exercising.”