Scientists recently discovered differences in how long-term consumption of cannabis and tobacco affect the lungs. A study published in the American Journal of Respiratory and Critical Care Medicine found that cannabis use is associated with hyperinflation of the lungs. This study was one of the first to provide evidence that cannabis smoking impairs transfer of gas, increases airway resistance, and decreases oxygen extraction. These symptoms may also be early signs of a severe form of emphysema colloquially known as “bong lung.”
This collaborative study between the University of Otago and Duke University involved the analysis of longitudinal data of 881 participants to track their lung function from age 18 to 45. Pulmonary function was assessed at age 45; spirometry (a breathing test), plethysmography (a test of how much air a person can hold in their lungs), and carbon monoxide transfer factor were assessed. The data indicated that cannabis smokers had significant pulmonary hyperinflation which reduces the lungs’ ability to extract oxygen from a breath. According to study co-author Dr. Bob Hancox, “the research found that prolonged cannabis use led to over-inflated lungs and increased the resistance to airflow to a greater extent than tobacco.” Chronic cannabis use specifically resulted in lower mid-expiratory airflow.
Some challenges of data analysis include teasing out data for participants who used both cannabis and tobacco and determining how much cannabis they typically consume. Among participants who smoke both tobacco and cannabis, there were strong associations with higher lung volumes and lower airway conductance. They also demonstrated lower gas transfer which suggests insufficient oxygen-carbon dioxide exchange. Dr Hancox observed that, “Cannabis users tend to smoke far fewer times a day than tobacco smokers and it is possible that the participants have not smoked enough cannabis for it to have a measurable effect on some aspects of lung function." Future research studies will further investigate the multiple factors that impact lung function.
Sources:
American Journal of Respiratory and Critical Care Medicine, Eureka Science News, Science Alert
