Cannabis Doesn't Improve COPD Exercise Endurance

Chronic obstructive pulmonary disease (COPD) is a progressive respiratory ailment, often tied to smoking, with characteristics of bronchitis and emphysema. The incurable disease remains the third biggest killer in the United States.

At first blush, it would seem almost obvious that individuals with COPD did not show improvement after inhaling vaporized cannabis. However, with real clinical data for cannabis’ true effects on human health being in scant supply, we should expect a range of studies and results to pop-up over the next several years, as more places begin to legalize the drug. The interesting part of the current study by investigators at McGill University is that while inhaled vaporized cannabis did not improve exercise performance and activity-related breathlessness in COPD patients, it also did not worsen their symptoms.

Findings from the new study – published recently in the Annals of the American Thoracic Society through an article titled “Effect of Vaporized Cannabis on Exertional Breathlessness and Exercise Endurance in Advanced COPD: A Randomized Controlled Trial” – did not find a difference between vaporized cannabis and placebo on lung volumes or heart rate at rest or during exercise. Nor did the study find that cannabis affected cognitive function, mood or psycho-activity.  

“We first became aware of the therapeutic potential of cannabis in managing COPD symptoms from patients themselves,” explained lead study investigator Sara Abdallah, a doctoral candidate in exercise physiology at McGill University. “We decided to pursue this study because patients were reporting symptomatic relief of their COPD symptoms after cannabis use.”

The burden of breathlessness in patients with COPD is high. Even when on optimal medication for their lung disease, many patients with COPD continue to suffer from disabling breathlessness at rest and while performing basic activities of daily living.

Interestingly, in the 1970s, controlled studies reported that smoking cannabis opened the airways of adults with and without asthma. More recently, a large observational study found a positive association between cannabis use and forced expiratory volume (the amount of air that can be forcefully exhaled in one second) and forced vital capacity (the total amount of air that can be exhaled after taking a deep breath).

“A series of studies conducted approximately 40 years ago demonstrated an acute bronchodilator effect of smoked cannabis in healthy and asthmatic adults,” the authors wrote. “However, the acute effects of vaporized cannabis on airway function in adults with advanced COPD remain unknown.”

In the current study, 16 patients with advanced COPD were recruited, all taking optimal medication for their lung disease: dual or triple inhalation therapy (long-acting muscarinic antagonist and long-acting beta2-agonist bronchodilator with or without an inhaled corticosteroid).

Participants were randomly selected to inhale a single dose of vaporized cannabis or a placebo before exercising on a stationary bike. Participants then “crossed over” to the other arm of the trial. Neither the researchers nor the patients knew when they were receiving the vaporized cannabis or the placebo.

Though the study did not find a clinically meaningful negative or positive effect of vaporized cannabis on breathlessness during exercise or on exercise performance, the researchers noted variability in responsiveness to the cannabis. For instance, after inhaling vaporized cannabis, breathlessness during exercise improved in 4 of the 16 patients. In the remaining 12 patients, breathlessness during exercise did not change or worsened.

Additionally, the study authors noted that trial results might not be generalizable because the number of participants was small and represented a relatively homogenous group of patients with stable, but advanced, COPD. Moreover, there were several factors that may have limited the therapeutic benefit of cannabis in the study, including the dose of cannabis used, that it was inhaled rather than taken orally and that it was administered only once and not repeated.

“Future clinical trials are warranted and should evaluate the therapeutic potential of various doses of vaporized and oral cannabis, including oils and pills, administered over longer periods of time in patients with mild to moderate COPD,” concluded senior study investigator Dennis Jensen, Ph.D., associate professor of kinesiology and physical education and a scientist in the Translational Research in Respiratory Diseases Program at McGill University.