Impact of Aerobic Exercise on Asthma Morbidity

Introduction: Asthma is a chronic respiratory disorder primarily driven by increased airway inflammation. It is one of the most prevalent chronic conditions affecting Canadians. It is the most common chronic illness affecting children and the fourth most common disorders affecting adults. In 2001, nearly 2.2 million (8.4%) Canadians were diagnosed as having asthma. More importantly, asthma is an escalating medical problem in Canada, e.g., between 1994 and 2001, there was a 40% increase in the number of Canadians with asthma. Not only is the prevalence of asthma increasing, but there has been a rapid rise in the morbidity and costs associated with asthma and its poor control. The WHO estimated that the global cost of caring for asthma exceeds that of AIDS/HIV and tuberculosis combined. Though recent guidelines have emphasized the importance of improving asthma control and quality of life, leading to huge amounts of resource being dedicated to this, more than 50% of adult patients with asthma remain poorly controlled. As current treatment strategies appear to be failing, it is important to target simple, cost effective interventions that are applicable for most patients with asthma and will increase overall levels of control and decrease asthma morbidity. There is evidence to suggest that aerobic exercise may improve asthma symptoms and control in children. In addition, there is evidence that exercise directly improves inflammatory and immune profiles in non-asthma patients, which may provide the mechanism by which exercise could improve asthma. However, there are no known studies that have systematically assessed the effects of aerobic exercise on asthma control, quality of life or immune function in adult asthma populations.

Objective: The primary objective of the current application is to assess the efficacy of aerobic exercise as an intervention to improve asthma control and quality of life in adult patients with asthma. The results of this study will provide data that will inform physicians and members of the Thoracic community about the benefits of exercise for asthma. The study will also assess potential inflammatory pathways by which exercise may elicit improvements in asthma morbidity. The results of this study should be available for the next Canadian Thoracic Society Canadian Adult Consensus Guidelines.

Methodology: The current proposal is for a study of aerobic exercise in sedentary patients with poorly controlled asthma. In addition to usual care, 52 patients will undertake supervised aerobic exercise. The exercise program will consist of 3 X 1hr sessions of supervised exercise per week for 12 weeks. The exercise routine, under medical supervision, will consist of 10 minutes of warm up exercises, 40 minutes of biking and/or walking (and eventually jogging), and 10 minutes of cool down exercises. These patients will be compared to a group of 52 patients who will follow their usual regimen, this group will be offered the exercise programme once they have completed the post assessments. For the primary outcomes (asthma control [Asthma Control Questionnaire], quality of life [Asthma Quality of Life Questionnaire]) and secondary outcomes (inflammatory profile) will be evaluated at baseline and after 12 weeks (the length of the treatment). To check the efficacy of the intervention both lung function, ambulatory peak flow, and exercise tolerance data will also be collected. Repeated measures analysis of covariance-type models with time (pre, post intervention) as the within subject factor, group (exercise, usual care) as the between factor, and sex, age, and asthma severity as the covariates will be used for the primary outcome variables. To assess the potential mechanistic role of inflammation on the exercise-asthma relationship a series of regression-like GLMs will be conducted.

It is hypothesized that: (1) The exercise intervention will result in clinically and statistically significant improvements in levels of asthma control and asthma quality of life; (2) The exercise intervention will result in clinically and statistically significant improvements in inflammatory profiles, with reductions in Th2 cytokines, and activation of inflammatory cells, and increases in Th1 cytokines; and (3) Changes in inflammatory profile will be directly linked to improvements in asthma measures.

We believe that the proposal will have great clinical significance for patient management. This project will be the first to systematically evaluate the benefits of exercise training on asthma control and quality of life in adult asthma patients. We anticipate that the results of this study will form the basis for new national and international guidelines and will provide an evidence-based background for physicians to prescribe aerobic exercise for patients with asthma.