The Dubious Result of a Randomized Controlled Trial (RCT)

Randomized controlled trials are widely viewed as the “gold standard” of medical evidence. But RCTs can be flawed in a variety of ways. They can have too few participants, they can be improperly randomized for a variety of reasons (not all relevant variables may have been identified or the protocol may not have been properly implemented). Forgive me, but the results of the RCT described below seem highly implausible. I believe that something about the RCT was flawed. Who can believe the result that those who engage in moderate exercise live shorter lives than those who only engage in very modest exercise. Common sense and many observational studies say the opposite, and such evidence should not be cavalierly dismissed.

(p. D6) Scientists have known for some time, . . ., that active people tend also to be long-lived people. According to multiple past studies, regular exercise is strongly associated with greater longevity, even if the exercise amounts to only a few minutes a week.

But almost all of these studies have been observational, meaning they looked at people’s lives at a moment in time, determined how much they moved at that point, and later checked to see whether and when they passed away. Such studies can pinpoint associations between exercise and life spans, but they cannot prove that moving actually causes people to live longer, only that activity and longevity are linked.

To find out if exercise directly affects life spans, researchers would have to enroll volunteers in long-term, randomized controlled trials, with some people exercising, while others work out differently or not at all. The researchers then would have to follow all of these people for years, until a sufficiently large number died to allow for statistical comparisons of the groups.

Such studies, however, are dauntingly complicated and expensive, one reason they are rarely done. They may also be limited, since over the course of a typical experiment, few adults may die. This is providential for those who enroll in the study but problematic for the scientists hoping to study mortality; with scant deaths, they cannot tell if exercise is having a meaningful impact on life spans.

Those obstacles did not deter a group of exercise scientists at the Norwegian University of Science and Technology in Trondheim, Norway, however. With colleagues from other institutions, they had been studying the impacts of various types of exercise on heart disease and fitness and felt the obvious next step was to look at longevity. So, almost 10 years ago, they began planning the study that would be published in October [2020] in The BMJ.

. . .

The scientists tested everyone’s current aerobic fitness as well as their subjective feelings about the quality of their lives and then randomly assigned them to one of three groups. The first, as a control, agreed to follow standard activity guidelines and walk or otherwise remain in motion for half an hour most days. (The scientists did not feel they could ethically ask their control group to be sedentary for five years.)

Another group began exercising moderately for longer sessions of 50 minutes twice a week. And the third group started a program of twice-weekly high-intensity interval training, or H.I.I.T., during which they cycled or jogged at a strenuous pace for four minutes, followed by four minutes of rest, with that sequence repeated four times.

. . .

The men and women in the high-intensity-intervals group were about 2 percent less likely to have died than those in the control group, and 3 percent less likely to die than anyone in the longer, moderate-exercise group. People in the moderate group were, in fact, more likely to have passed away than people in the control group.

For the full story see:

Gretchen Reynolds. “Working Out With Intensity.” The New York Times (Tuesday, December 29, 2020 [sic]): D6.

(Note: ellipses, and bracketed year, added.)

(Note: the online version of the story was updated Nov. 10, 2021 [sic–yes 2021], and has the title “The Secret to Longevity? 4-Minute Bursts of Intense Exercise May Help.” Where the wording of the versions slightly differs, the passages quoted above follow the online version.)

The study published in The British Medical Journal (BMJ), and mentioned above, is:

Stensvold, Dorthe, Hallgeir Viken, Sigurd L. Steinshamn, Håvard Dalen, Asbjørn Støylen, Jan P. Loennechen, Line S. Reitlo, Nina Zisko, Fredrik H. Bækkerud, Atefe R. Tari, Silvana B. Sandbakk, Trude Carlsen, Jan E. Ingebrigtsen, Stian Lydersen, Erney Mattsson, Sigmund A. Anderssen, Maria A. Fiatarone Singh, Jeff S. Coombes, Eirik Skogvoll, Lars J. Vatten, Jorunn L. Helbostad, Øivind Rognmo, and Ulrik Wisløff. “Effect of Exercise Training for Five Years on All Cause Mortality in Older Adults—the Generation 100 Study: Randomised Controlled Trial.” BMJ 371 (2020): m3485.

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