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We’ll say it again, this time in French: La corrélation n’implique pas la causalité


2 Star

Just 30 minutes a day: Regular exercise relieves asthma symptoms

Our Review Summary

iStock_000021196165_SmallThe news release from Concordia University in French-speaking Montreal highlights a new study published in BMJ Open Respiratory Research, which explored the correlation between regular exercise and patients’ control of asthma symptoms. The release makes good use of direct quotes from the study’s lead author, who brings color into the piece. On the other hand, it lacks a thorough discussion of the study’s important limitations and inappropriately suggests that exercise is responsible for the benefits seen in those who exercise more — e.g. the headline “Regular exercise relieves asthma symptoms.” That’s a conclusion that simply can’t be drawn based on this observational study, which showed a correlation only and cannot demonstrate cause and effect.


Why This Matters

This study seeks to address the relationship between physical activity and symptoms in patients with asthma. The study interviewed individuals with asthma recruited from a hospital’s population with this condition and asked them questions about activity and symptom control. The study reported that those who were more physically active also reported better control of their asthma. This resulting news release then goes on to imply that this proves that we should encourage patients with asthma to be more physically active. Though this may be true, the study doesn’t actually show this. Only by taking those patients who are inactive and then randomly assigning them to an activity program or continued inactivity can we know whether the claims made in the release are true. It may simply be that those who had less severe asthma were able to be more active. The attenuation of the reported findings when controlling for differences among those who were more or less active supports this. While efforts to promote physical activity should be commended, such advice shouldn’t imply benefits that aren’t well-established without clearly noting limitations in the evidence.


Does the news release adequately discuss the costs of the intervention?

Not Applicable

Physical activity was broadly defined in the study and included activities such as walking, dancing and swimming. We rate this Not Applicable, since cost is not a major factor here. But we need to keep in mind that this piece was recommending 30 min per day of activity. That’s 3.5 hours per week. This is time that could be spent doing other things (including paying work) and there may be a cost – either positive or negative – associated with it. In theory, if exercise does in fact reduce asthma symptoms, one could argue that patients with asthma who exercised would have lower costs of care for things such as emergency visits. But this, of course, is unproven.

Does the news release adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

The news release reported the benefits of physical activity in relative numbers, stating “those who engaged in optimal levels of physical activity on a regular basis were nearly two-and-a-half times more likely to have good control of their symptoms, compared with those who did no exercise.” To which we respond: Two-and-a-half times more than what? While the statistic is technically accurate, there is no translation of this into an absolute number that a reader could use to interpret the result – such as x% of those who exercise reported adequate control versus y% of those who did not. The news release also prefaced this statement with “Results were overwhelmingly clear.” But many questions were left unanswered. What does it mean to have “good control of their symptoms?” And who exactly experienced these benefits? Does “optimal levels of physical activity” mean 30 minutes every day? More clarification would have been welcome here.

Does the news release adequately explain/quantify the harms of the intervention?


The news release points out some precautions people need to take before exercising. The study’s lead author explains that patients should use “releaver medication” (sic) before they exercise and adds they should take the time to cool down afterward. He also says people could exercise indoors during the winter months, since cold air provides another trigger for asthma symptoms. It would have also been helpful to note that any physical activity triggers asthma symptoms in some people. In these cases, patients may have to take medicines before they exercise. The National Heart, Lung and Blood Institute recommends easing into physical activity with a warm-up period and also wearing a mask or scarf over the mouth when exercising in cold weather. More detail would have been appreciated here, but we feel the news release had enough for a Satisfactory rating.

Does the news release seem to grasp the quality of the evidence?

Not Satisfactory

The news release does not point out any limitations of this observational study and uses inappropriate language to describe the findings. The headline — “Regular exercise relieves asthma symptoms” — suggests that exercise causes a reduction in asthma, which is something this study couldn’t show. Why doesn’t this study demonstrate causality? Imagine that patients who report exercising more have less severe asthma. Maybe it isn’t the exercise that matters, but rather the underlying mildness of the symptoms that allows them to exercise more than those with more severe symptoms. In theory, one could control for this by knowing their lung function tests, but we don’t have that information. The information collected can’t fully address this source of bias and should lead to much greater caution about interpreting the results than is shown in this news release.

Does the news release commit disease-mongering?


The news release does not engage in disease mongering. A little context could have been helpful, however, such as what exactly asthma is, what triggers the condition and how many people suffer from it. According to the original research report, asthma remains poorly controlled in the majority of patients: 60 percent of Canadian and 75 percent of European patients report not having their asthma symptoms under control. These patients often use more health care services, perhaps driving up costs for the sector, and also experience greater functional impairment. Asthma is a long-term disease with no cure, and the costs of buying pills and inhalers to control the condition could add up during the lifetime of a patient. Any alternative that could help patients control their asthma and maybe also save money on the side would be newsworthy, since more than 25 million people in the US are known to have asthma – in which 7 million are children, according to the National Heart, Lung and Blood Institute.

Does the news release identify funding sources & disclose conflicts of interest?


The news release states the funding sources, which were grants from the Social Science and Humanities Research Council, Fonds de recherche du Quebec – Sante, the Canadian Institutes of Health Research and the Michel Auger Foundation of Hopital du Sacre-Coeur de Montreal. No conflicts of interests were declared, both in the original journal article and in the news release.

Does the news release compare the new approach with existing alternatives?

Not Satisfactory

A bit of context was missing here. The news release quotes the study’s lead author saying, “It would be great to see physicians recommending physical activity to patients with asthma, alongside traditional pharmacological treatments,” but the news release doesn’t detail what those drugs are. According to the National Heart, Lung and Blood Institute, asthma is treated with two types of medicines: long-term control and quick-relief medicines. Long-term control medicines, like inhaled corticosteroids, help reduce airway inflammation and prevent asthma symptoms. Quick-relief inhalers, or “rescue,” medicines relieve asthma symptoms that may flare up.

Another problem here is that this study really doesn’t provide anything to support the author’s desire to see physicians recommending more exercise. Should we simply tell patients with severe asthma to exercise? Or do we need to treat them in a way that permits them to exercise safely? This study isn’t designed to answer these questions, so it really can’t compare alternatives. We would have given credit if the release had simply said that “only interventional studies designed to examine the combination of physical activity and medication recommendations can determine how best to see if this observation can lead to better patient outcomes.”

Does the news release establish the availability of the treatment/test/product/procedure?

Not Applicable

The availability of exercise is not in question.

Does the news release establish the true novelty of the approach?

Not Satisfactory

Studies have already been conducted looking into the link between increased physical activity and better health outcomes for asthma patients, such as this 2009 study and another one from 2009. In general, researchers have found that higher levels of physical activity are beneficial – both in terms of better health outcomes and decreased use of health care services – for those suffering from asthma. The original journal article from this study states this was the first time researchers have looked into seasonal variations in physical activity and its correlation with asthma control. Patients who undertook physical activity during the winter months (rather than the summer) had better control of their asthma, the research report emphasized. Although this point was touched upon in the news release, it does not explicitly state what was novel in the research or what it brings to the existing body of literature, which is why we give the news release a Not Satisfactory rating here.

Does the news release include unjustifiable, sensational language, including in the quotes of researchers?

Not Satisfactory

This point was also touched upon in the “Quality of Evidence” section. We feel some of the wording used in the news release could have been toned down, such as “simple antidote,” “overwhelmingly clear,” “significant reduction” and a “whopping 245.” The release also incorrectly implied causality rather than association with its choice of words — e.g. “relieves symptoms” in the headline. We would recommend more neutral and even cautionary language when reporting the findings of a study with significant limitations such as this one.

Total Score: 3 of 8 Satisfactory


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