The association between regular cannabis use, with and without tobacco co-use, and adverse cardiovascular outcomes : cannabis may have a greater impact in non-tobacco smokers
Theresa Winhusen, Jeff Theobald, David C. Kaelber, and Daniel Lewis
The American Journal of Drug and Alcohol Abuse, 2019
Background : Understanding the potential impact of cannabis use on cardiovascular health is increasingly important as cannabis use rises in the U.S.
Objectives : This study evaluated the associations between regular cannabis use, with and without tobacco co-use, and cardiovascular outcomes.
Methods : Analysis of a limited dataset obtained through IBM Watson Health Explorys, a platform integrating electronic health record data. Matched controls using Mahalanobis distance within propensity score calipers were defined for: 1) cannabis-using patients (n = 8,944; 43% female); and subgroups of cannabis-using patients: 2) with an encounter diagnosis for tobacco use disorder (TUD; n = 4,682); and 3) without a TUD diagnosis (non-TUD; n = 4,262). Patients had ≥1 blood pressure measurement and blood chemistry lab result in the MetroHealth System (Cleveland, Ohio). Cannabis using patients had an encounter diagnosis of cannabis abuse/dependence and/or ≥2 cannabis-positive urine drug screens. Control patients, with no cannabis-use-documentation, were matched to the cannabis-using patients on demographics, residential zip code median income, body mass index, and, for the total sample, TUD-status. Outcomes were encounter diagnosis (yes/no) of cerebrovascular accident (CVA), heart arrhythmia, myocardial infarction, subarachnoid hemorrhage (SAH), and all-cause mortality.
Results : TUD-patients had the greatest prevalence of cardiovascular disease, regardless of cannabis- use indication. In the total sample and non-TUD subgroup, regular cannabis use was significantly associated with greater risk for CVA, arrhythmia, SAH, and mortality. In the TUD subgroup, regular cannabis use was significantly associated with greater risk for arrhythmia and SAH.
Conclusions : Cannabis use is associated with significantly greater risk of adverse cardiovascular diagnoses and overall death, particularly in non-tobacco users.
KEYWORDS : Cannabis; cardiovascular; electronic health record (EHR); mortality
Cannabis use in U.S. adults has increased significantly in recent years (1,2). There is a dearth of high-quality research on the effects of cannabis use on health (3) and, in the absence of scientific evidence,
there is a tendency to perceive cannabis as being harmless or even helpful (4,5); this is important since research has found that the perception of no risk from cannabis use is associated with increased use (6). As more U.S. states legalize cannabis, it becomes increasingly important to understand the potential impact of cannabis use on health so that adults can make informed choices about its use.
Heart disease is the leading cause of death in the U.S (7). Animal and in vitro research suggests that
cannabis may have a negative impact on cardiovascular functioning (3,8,9). Recent reviews of the clinical
literature have concluded that existing research is insufficient for evaluating the association between cannabis use and adverse cardiovascular outcomes (3,8). Limitations of past research include reliance on self-reported cannabis use, the use of crosssectional rather than longitudinal designs, failure to control for potential confounding factors, the use of study samples in which harm is less likely to be detected (i.e., younger participants, infrequent cannabis users) (8), and the failure to disentangle the effects of cannabis from tobacco smoking (3,10). The latter is of importance since tobacco smoking is a primary cause of cardiovascular disease (11) and there is a high prevalence of tobacco smoking among people with cannabis use disorder (CUD), which has been estimated to be 47% (12).
The present study evaluated the association between regular cannabis use, with and without tobacco co-use, and cardiovascular outcomes using a method that addresses many of the limitations of past research (13). This approach included using EHR data, rather than self-report measures, of cannabis use and adverse cardiovascular outcomes, use of a multi-year dataset, which allows detection of effects that may take several years to develop, large sample sizes, and the use of rigorous matching and analytic procedures to control for potential confounding factors (e.g., age, race, ethnicity, socioeconomic
status, other substance use, etc.). We predicted that a positive association would be found between regular cannabis use, with or without tobacco-co-use, and adverse cardiovascular outcomes.