Risk of Heart Failure-related Events in Patients Exposed to Medical Cannabis: A Longitudinal Cohort Study

This study examined the association between the authorized prescription of cannabis and heart failure (HF) events.

We conducted a retrospective cohort study of patients who received an authorized prescription of cannabis in Ontario cannabis clinics between 2014-2019 and controls selected from the general population of Ontario.

Ontario's health administrative data and clinical data from the cannabis clinics were used. Inverse probability of treatment weights based on propensity scores were used to minimize confounding between cannabis exposure and the study outcomes. Weighted Cox proportional hazards regressions measured the association between exposure to cannabis and ED/hospitalization for HF (primary outcome), and a secondary outcome that extended the primary outcome by including physician claims for HF.

Among 54,006 patients exposed to cannabis and 161,265 controls, 39% were aged ≤ 50 years, and 55% were female. For the primary outcome, incidence rates for ED visits/hospitalization due to HF were 5.87/1000 person-years (95%CI: 5.72-6.03) in the cannabis group and 5.14/1000 person-years (5.05-5.22) in the control group.Patients exposed to cannabis had a higher risk for the primary outcome with a hazard ratio of 1.15 (95%CI: 1.06-1.25). For the secondary outcome, incidence rates were 18.99 (95% CI: 18.55-19.44) in the cannabis group and 16.69 (95% CI: 16.46-16.93) for controls; with a hazard ratio of 1.13 (95% CI: 1.08-1.19).

The results suggest a higher risk of heart failure-related events, including emergency department visits, hospitalizations, and outpatient consultations, among patients who were authorized cannabis for medical purposes.