Daniel Sanabria, psychologist: “The best predictor of professional success is not cognitive performance, it is that your parents will have money” | Health & Wellness

Exercise can help and increase your thinking ability, Scott McGinnis, a neurologist at Harvard Medical School, said in a press release from his institution. “For healthy people, regular exercise can improve brain function throughout life, not just after training,” he writes in an article published by american scientist David Jacobs, a professor at the University of Minnesota. The list of researchers and popularizers who take for granted the cognitive improvement of physical exercise is long and a good number of studies seemed to support this position. However, a few days ago, Daniel Sanabria Lucena (Bordeaux, France, 46 years old) and his team published a review of studies in the journal Nature Human Behavior in which they included 109 works in which they had more than 11,000 people in which a positive effect of exercise on cognition had been found. After analyzing them in depth, they found that this effect did not have strong evidence to support it.

“Knowledge on this subject is not advanced enough to be able to make recommendations as forceful as those that are made,” he says in an interview by video call, and recalls that his group “is not the first to have said it.” Adele Diamond, of the University of British Columbia in Vancouver, also states that “aerobic exercise, resistance training, or yoga have not been shown to improve higher cognitive functions,” including the ability to plan, make decisions or working memory. “But we don’t talk about mental health, which is a different topic,” Sanabria points out.

Ask. Studies like yours show the difficulty of offering definitive prescriptions on many aspects of health. Do you think that people can learn to live with this uncertainty and not accept clear but baseless advice?

answer In the first place, I believe that scientific education is needed in the population, starting at school, so that people understand how science works. It is important, however, that researchers have our biases, interests and prejudices. For some, science has become a kind of religion, a source of absolute certainties, and it doesn’t really work that way. People want to know what they have to do to take care of their well-being, including their mental one. We want simple recipes. But, on most occasions, giving recipes is complicated, to which is added, as we saw in the pandemic, that we are not very tolerant of uncertainty.

In my own classes, I remember discussing two conflicting theories about a phenomenon, and one person asked me: So what am I to believe? I told them that science is not about believing, it is about discovering theories and accumulating evidence, which can be more or less solid and conclude in favor of one hypothesis or another.

P So, as your students would say, what do we do with the exercise?

R. In this particular case, from what we know, what I would say is if exercising makes you feel good, do it. Because there is also very solid evidence about the benefits for physical health.

P How do you get all these studies that have led us to believe that exercise had a positive effect on cognition?

R. In the last two decades there has been a growing interest in this subject, looking for benefits of physical exercise beyond physical health. Studies have been done looking for relationships between the level of physical activity of a group of people, in some cases with thousands of participants, their level of cardiovascular fitness and cognitive performance. These studies show confirmation, but no significant causal connection. For this reason, intervention studies have been carried out, where they randomly assign people to the experimental group, who perform physical exercise, and other people to the control group, who do not perform physical exercise, or who perform an activity that, they suppose, will not have an impact at the cognitive level. The evidence obtained from this type of study is what is frequently used to affirm that physical exercise improves cognition. We have analyzed 109 of these studies, those that focus on the healthy population, and the conclusion is that the evidence on these supposed cognitive benefits is not conclusive at all. In fact, we think that intervention studies may not be the best tool to study the possible effects of regularly practiced exercise at the cognitive and brain level, and that it would be better to obtain evidence from longitudinal studies. If we get conclusive evidence about the existence of these effects, it would be the question of “why”, but that is enough for another interview. And then there is that, sometimes, the results are not published when the desired effect does not come out.

P So, are there results that, because they are more attractive, are searched for more and come out more?

R. A paradigmatic example is bilingualism, the advantage of being bilingual at a cognitive level. Between 2000 and 2010, there was a boom of articles showing that people who spoke more than one language were more cognitively competent than monolinguals. I have come to see examples of bilingual schools selling bilingualism as a tool to improve the cognitive ability of their students. However, papers appeared that showed a publication bias [la tendencia a que se publiquen más los resultados positivos que los nulos], especially in groups that were quite prolific in that field. In addition to this, in this topic of bilingualism and cognitive performance, studies with quite large samples and null results have emerged in recent years.

In the case of physical exercise, we have carried out several works that, at first glance, could show counterintuitive results. One on mental fatigue in physical performance. Today there is literature that says that if you do a mentally demanding task just before doing physical exercise, you will perform worse physically than if you do something less demanding before. In sports science it seemed something assumed. We tried to replicate a classic study in this line and obtained null results, and then we began to question the quality of the evidence. We started looking at the literature and the studies used very small samples of subjects. We did a meta-analysis and, indeed, there were very small samples, which increases the probability of finding a false positive, poor-quality studies, and publication bias.

And another line of research in which we have worked is the one that looks for the effects of electrical brain stimulation by direct current, of low intensity, to improve physical and sports performance. There was even a company that sold a device that stimulated the brain to improve physical performance. We did an empirical study, trying to replicate previous results and, again, we found a null result. We did a meta-analysis, and again we found studies with very small samples, publication bias, and inconclusive literature.

That being said, the results of our investigations that I have committed to here do not mean that these effects do not exist, since the absence of evidence of an effect is not evidence of the absence of an effect. What they indicate is that, with the studies available so far, nothing can be concluded about these phenomena. More research is needed.

P Does the way people are chosen to participate in the studies influence the results?

R. It can have a significant impact, yes. For example, imagine a call for participation is made that says they are looking for older people for a study that wants to look at the effects of exercise on cognitive and brain performance in preventing cognitive decline. Who is going to sign up? It must be likely that they are people who have an interest and expectation that exercise is going to have an effect on their brain. And this group, in many studies, is compared to one of the so-called “waiting list”, which continues its normal life, which does nothing. They don’t buy that in medicine anywhere. You always have to have a placebo group, because you know that the expectations about the effect of a drug can already have an effect. In addition, in our recent review study on the effects of exercise at the cognitive level, we have seen that in many studies, people in the experimental group, who receive physical exercise training, tend to start from a lower point in their cognitive performance than the people included in the control group, who did not receive the physical exercise intervention. Therefore, the experimental group has more room for improvement than the control group. That this difference between the groups before starting the intervention tends to be in favor of the experimental group in many studies could be another indicator of publication bias.

P In the explanation of the effects of psychological results, does too much focus on the effects on the brain and little on the context?

R. One of the dangers of this topic of measuring the effects of something, and it goes for the exercise, the consciousness or whatever, it is that very relevant factors are usually ignored, which are context factors. The most predictor of academic performance and subsequent professional success is not cognitive performance, it is the sociocultural context. That your parents have money. Some ways of interpreting the results send us a subtle message that places responsibility on the individual. If you’re fat it’s your fault, and it has nothing to do with being surrounded by junk food, if you don’t exercise and you get sick it’s because of your lack of will… I think that’s dangerous.

P Although that is true, it is not incompatible with limiting the amount of junk food accessible and telling people that part of their health is in their hands, going for a run or trying to buy less ultra-processed food.

R. Totally agree, it’s not incompatible. And I don’t want it to be the message of our work. I recommend people exercise, of course. But, above all, if you plan to enlist your son or daughter to practice a sport or play chess, do it to see if they like it, but not to look for an effect on their mind, because the effects, if they exist, are small and, to this day, the scientific evidence is not conclusive in this regard. And I think it’s important to stress again that not all of the responsibility for physical and mental well-being should rest with the individual.

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