It’s not a surprise that people are confused about the best lifestyle choices to improve and maintain health. Whether the recommendations are for diet or exercise, it seems that every three months there is contradictory advice from the medical community and the people who report on it. Eat eggs…don’t eat eggs. High carb diet…low carb diet.

In part, the flood of seemingly contradictory advice is a consequence of the how the media reports on medical research. This seems especially true when medical research contradicts conventional or existing wisdom. Scientific studies on controversial topics are immediately picked up and translated into extravagant claims by the media. These inaccurate and misleading stories gain traction through social media megaphones and are promoted by people that would rather not have to follow the existing medical advice. The advice can justify the unhealthy habits of the non-adherents. An even worse consequence is that these constantly contradictory reports in the media can scare those that had adhered to good behaviors into stopping those behaviors.

Will running extend or shorten your lifespan?

Will running extend or shorten your lifespan? (Image source: Wikimedia)

It was just this past week that several of my friends on Facebook (and in real life) alerted me to the latest sensational and woefully misleading headlines. “Running Too Much May Be as Bad as Sitting Around”, and other similar titles appeared in numerous journals and magazines last week (here, here, here, here). All of these articles report essentially the same thing. You thought running was good for your health, but now researcher say they have data to prove you wrong.

The problem with these headlines are really two fold: one, the study they are basing their information on is inherently flawed and two, other much better studies show the opposite results. Lets start with the first point. The particular study that generated the above headlines was published in the Journal of the American College of Cardiology (JACC). It is actually a part of a bigger study called the Copenhagen Healthy Heart study that had been going on for more than 10 years. During this time, researchers tracked more than 5000 individuals living in Copenhagen, noting all of their behaviors, changes in mortality risk factors, and ultimately mortality (as the study’s final end point).

Within this larger group, was a group of regular runners comprised of 878 people. They divided this larger group into subgroups of runners that did either light running, moderate running, or strenuous running, and compared the mortality rates between these three groups. Fortunately for the runners, but unfortunately for the scientists, there were only 17 deaths among the 878 runners in the last 10 years of the study. With so few deaths, it was impossible for the scientists to make any robust conclusions. Instead they matched these runners to similar (age, weight, smoking) non-runners and found, not surprisingly, that those that did light and moderate amounts of running had a significantly lower risk of death (Figure 1).

Figure 1. This study found that the risk of death was higher in strenuous joggers than in sedentary people or light/moderate runners. But before you believe their conclusions, look at the subject number and the confidence intervals in the strenuous runner group!

What was a surprise, and led to the sensationalized media headlines, was the strenuous runner group did not have a lower risk of death than those so-called “couch potatoes”. On first glance this looks bad for those of us that run a lot (myself certainly included), but looking further into the data, it’s easy to see why the researchers saw no difference:  there were only 40 runners in the strenuous runner group (10x fewer than the light and moderate runner groups). This is an inappropriately low number of subjects to make any conclusions from, no matter what the conclusion. The lack of robustness of their data caused by the small subject number in the strenuous group is indicated by the huge confidence intervals seen in the strenuous group compared to the other runner groups, which had more subjects (Figure 1). So all it took was the deaths of two runners in the strenuous group during the 10-year follow-up period to make that group’s percent likelihood of dying similar to that of non-runners.

The take home message is that this study had too few subjects, and it disagrees with several published studies with much larger numbers of subjects. One example, also published in the JACC, found that the amount you run results in a proportional reduction in mortality (Figure 2). That particular study looked at 55,137 adults. In a second study of Finnish twins with more than 16,000 subjects published in the Journal of American Medicine Association, scientists found something similar. The group of most strenuous exercisers had the same risk of mortality as the occasional exercise group, and both groups had lower mortality rates than non-exercisers.

Figure 2. This study, which was also published in JACC, had a much larger subject population and found that running reduces the risk of mortality. (From Lee et al. 2014; JACC)

Figure 2. This study, which was also published in JACC, had a much larger subject population and found that running reduces the risk of mortality. (From Lee et al. 2014; JACC)

I could go on, but will instead refer you to an excellent and detailed rebuttal in the mainstream media that summarizes where the entirety of the research stands. I recommend this article by Alex Hutchinson in Runners World (or this article in the NY Times) in which he fully admits that there is likely an upper limit of beneficial exercise, just not the one the current study claims. His article is well balanced and takes into consideration all pre-existing studies, something the authors of the JACC study clearly didn’t. In their comments to the media, the authors gave sensationalized quotes to make their results look much more robust than they actually were, and unfortunately, journalists reported this without adequate investigation of the claims.

I am not sure which is crazier, the fact that these scientists are quoted as saying as much, or that there are journalists that don’t look into the details before reporting on a study with serious implications such as this. So what’s needed? There are a few answers: scientific literacy, healthy skepticism around results that contradict what is generally accepted in a field, and scientists not overselling our work merely to generate buzz. At the same time, we can’t allow ourselves to become dogmatic to a point where new findings are ignored and ostracized for merely being different or going against previously published results. So, in the end, it’s the job of scientists, journalists, and the public to provide and understand the context of scientific studies and how they are reported.