Study Finds Cannabis Smoking Does Not Carry Same Risks As Tobacco

Cannabis smoking is not associated with an elevated risk of chronic obstructive pulmonary disease (COPD) even among those possessing a clinically high risk for developing the disease, according to a study, Impact of Marijuana Smoking on COPD Progression in a Cohort of Middle-Aged and Older Persons, published in the journal of the COPD Foundation. 

COPD, which refers to a group of diseases that cause airflow blockage and breathing-related problems including emphysema and chronic bronchitis, makes breathing difficult for the 16 million Americans with this disease. 

Older Adults, Longterm Smokers

Researchers at the University of California Los Angeles (UCLA) evaluated the relationship between cannabis use and the development of COPD in a cohort of older subjects who either smoked cannabis now or who smoked cigarettes on a regular basis in the past.

The researchers determined that neither former nor current cannabis smoking was associated with evidence of COPD progression or its development.

Background: Limited data are available regarding the impact of marijuana smoking impact on the development or progression of COPD in middle-aged or older adults with a variable history of tobacco cigarette smoking.

Methods: Researchers divided ever-tobacco smoking participants in the Subpopulations and Intermediate Outcomes in COPD Study (SPIROMICS) into three groups based on self-reported marijuana use: current, former or never marijuana smokers (CMS, FMS or NMS, respectively). Longitudinal data were analyzed in participants with ≥2 visits over a period of ≥52 weeks.

Measurements: Researchers then compared CMS, FMS and NMS, and those with varying amounts of lifetime cannabis use. Mixed effects linear regression models were used to analyze changes in spirometry, symptoms, health status and radiographic metrics. All models were adjusted for age, sex, race and baseline tobacco smoking amount.

Spirometry tests are commonly used to help diagnose lung conditions, like asthma and COPD, by measuring the amount of air someone can breathe out in one forced breath. This is done with a device called a spirometer, which has a mouthpiece the patient can breathe into.

“In [this] cohort of ever-tobacco smokers of ≥20 pack-years with established COPD or at risk of developing COPD followed over an average of more than four years, a history of current and/or former smoking of marijuana of any cumulative lifetime amount was not found to be associated with a significantly deleterious impact on progression of COPD,” the authors reported.

“Among ever-tobacco smokers in the same cohort without COPD at enrollment, self-reported current and/or former concomitant marijuana smoking, including heavy marijuana smoking, was not found to be associated with an increased risk of subsequently developing COPD.”

The findings are consistent with prior studies concluding that cannabis smoking, even long-term, is not positively associated with COPD, lung cancer, or irreversible airway damage, per the study.

Younger Adults: Similar Findings, Different Study

A similar longitudinal study was undertake  recently at the University of Queensland, Australia and published in Respiratory Medicine with a cohort of 1173 young adults between 21 and 30 who smoked cannabis, tobacco, both or nothing over 9 years found an association between tobacco smokers and reduced airflow. Those who smoked cigarettes alone, or cigarettes with cannabis smoking, had reductions in their airflow, though cannabis did not add to these reductions; cannabis smoking alone did not reduce airflow or seem to impact lung functioning. Even after 9 years of use, cannabis smoke exposure did not seem to impact the lungs.

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