Tuesday January 3 2012
The link between exercise and school grades needs more study
BBC News has reported that there is “strong evidence of a link between exercise and academic performance”. The news service says that a review of previous research found a link, which could be due to exercise increasing the flow of blood and oxygen to the brain.
The news was based on a Dutch review that systematically assessed 14 studies. These studies had previously looked at a possible link between the amount of exercise done by a child or adolescent and their academic ability. The researchers conclude that the studies show an association between exercise and academic achievement, but they stress that only two of the 14 studies could be considered to be of high quality. It is, therefore, not possible to determine the extent to which exercise is associated with academic performance, and the authors do not provide any numerical data to support the relationship.
As the researchers themselves have highlighted, there is a need for further high-quality studies to be performed to clarify any potential link. In particular, none of the studies used an objective measure of physical activity, so it is not clear whether the exercise estimates in existing studies have been accurate.
Where did the story come from?
The study was carried out by researchers from Holland’s EMGO Institute for Health and Care Research and Vrije University. No sources of funding were reported. The study was published in the peer-reviewed medical journal Archives of Pediatric and Adolescent Medicine.
The BBC reported the research well, highlighting that there is a need for further research into the relationship between physical activity and academic performance. The news service also notes that one of the limitations of this research is the absence of an objective measure of how much exercise the children and adolescents were doing.
What kind of research was this?
This was a systematic review that assessed the relationship between physical activity and subsequent academic performance.
The researchers say they are interested in this area as there is an increasing body of literature suggesting that physical activity can positively affect mood and may also enhance brain function and performance. The researchers wanted to look at all of the available evidence investigating this link. The researchers selected prospective studies that had assessed physical activity and then followed the participants over time to see the association between this activity and their subsequent academic performance.
What did the research involve?
The researchers searched four medical and sports science databases for articles published between 1990 and 2010 that had assessed physical activity and academic achievement in people under 18 years of age.
They included prospective studies that described at least one physical activity or physical fitness measurement during childhood or adolescence, and recorded at least one academic achievement or cognition measure during childhood or adolescence.
The reviewers assessed the quality of the methods used in the articles they selected, grading the evidence they provided. In total, the reviewers included 14 studies in their review.
Eight of the studies required children to self-report their athletic participation. Other studies relied on reports from teachers, parents and school administrators. Four studies had assessed the impact of a school exercise programme. These studies did not assess the amount of physical activity performed, but one programme intended to increase participants’ exercise time. All of the studies had used subjective measures of physical activity rather than objective measures, which would have been preferable.
Four studies assessed academic achievement by self-reported school grades, seven by cognitive test scores and three had used both measures.
What were the basic results?
The researchers found 12 relevant studies performed in the US, one in Canada and one in South Africa. These had sample sizes ranging from 53 to 12,000 participants aged between 6 and 18 years. The follow-up in the studies ranged from eight weeks to more than five years. Two of the studies were considered to be of high methodological quality according to their scoring system.
The researchers first looked at nine studies that had compared subgroups of students on the basis of their participation in sports: athletes with non-athletes, or students who participated in PE or organised sports in school with those who did not. They found that the results from these studies did not consistently show a relationship between sports participation and academic performance.
Three studies, including one of high methodological quality, assessed time spent doing exercise. All three studies found that higher physical activity was associated with better academic performance.
Three of the four studies that had assessed exercise programmes in schools found that exercise was associated with better academic performance than a control programme.
The researchers then combined the data from all 14 studies and reported that this initially provided “strong evidence of a positive relationship between physical activity and academic performance”. They note that only two of the studies were of high methodological quality, but do say that these also support the relationship. They also disregarded the studies of low methodological quality in the final evidence synthesis, which once again supported a relationship.
The review did not report any numerical data, such as how much exercise was required to improve academic performance. Nor did it quantify how variable the studies’ data were.
How did the researchers interpret the results?
The researchers say that relatively few studies of high methodological quality have explored the relationship between physical activity and academic performance. Despite this, they say that they have “found evidence that participation in physical activity is positively associated with academic performance in young people”.
The researchers note that only two of the studies were of high methodological quality, but do say that these also support the relationship. The relationship was also evident during the final evidence synthesis, in which they disregarded the other studies of low methodological quality.
This systematic review of prospective studies has found evidence of an association between physical activity and academic performance through examining the results of 14 previous studies. The strength of this association was not quantified. The researchers acknowledge that the 14 studies they included were largely not of high methodological quality and had various limitations:
- The studies did not include an objective measure of how much physical activity the students did. Rather, they relied on the students to self-report activity or assessments by parents or teachers, which may not fully reflect the amount of exercise the children did.
- The included studies were very different in their design and it was not possible to perform a meta-analysis combining their results. Instead, the researchers used an approach where they reported the number of studies that had found a positive effect of exercise and the number that had shown no effect. This approach can make the studies seem more similar than they actually are.
- It is not clear how the final conclusion – that overall there was an association between exercise and academic performance – was reached. No statistical tests to determine the strength of the association were performed and it is unclear whether the findings were down to chance. Counting the number of studies with positive findings can be problematic as ‘publication bias’ may have occurred. This means that studies with positive results are more likely to be published than studies with negative results.
- The studies did not assess several possible confounding factors. For example, both the amount of exercise a child takes and their academic performance may be affected by their socioeconomic status and upbringing.
The main conclusion that can be drawn from this research is that there has, so far, been a limited number of high quality studies that have assessed how the amount of exercise a child or adolescent takes is associated with their academic performance.