Impact of marijuana on adherence, risk factor control and cardiovascular events

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Marijuana is the most common illegal substance used worldwide with increasing use among the US population. While the physical harms of marijuana outside of its neurocognitive effects have been inadequately studied, there is a perception that it is safe and has health benefits. One area of particular concern is the effect of marijuana use on cardiovascular health. Several sources of data are contributing to an emerging hypothesis that marijuana use independently increases the risk of cardiovascular events. In addition, marijuana use adversely impacts memory, cognition and motivation. Therefore it is plausible that marijuana use is associated with poor medication adherence and poor risk factor control and indirectly impacts cardiovascular health. To address the extensive gap in the literature on the potential cardiovascular harms of marijuana, we propose to construct a cohort of patients 65 to 67 years of age in the Veterans Health Administration (VA) with established coronary artery disease (CAD) using merged national VA and Medicare data. Specifically, we propose to use text processing methods to review medical record notes and identify mentions of marijuana use to preliminarily categorize patients into marijuana users and non-users. We will then perform an in-depth telephone health interview with each patient to ascertain exposure history (e.g., marijuana use, tobacco use, substance abuse, depression, self-reported health, and physical activity) and will compare the cardiovascular events among 860 current marijuana users and 860 non-users. We will leverage the vast amount of data available in VA databases to refine baseline patient characteristics. For this revised application, we conducted a successful pilot study and demonstrated the feasibility of our patient identification and recruitment strategy. We have three goals in this proposal: (1) to examine the baseline differences between marijuana users and non-users, (2) to examine the effect of marijuana use on medication adherence (e.g., beta blockers) and risk factor control (e.g., blood pressure) and 3) to examine if marijuana use independently increases the risk of cardiovascular events among patients with established CAD even after adjusting for medication adherence, risk factor control and baseline differences. We will use propensity score methods to address these aims. Very little is known about the physical harms of marijuana. Any effect of marijuana on cardiovascular health would have a substantial public health impact given that cardiovascular disease is the main cause of morbidity and mortality in the US. This proposal will help public health leaders prepare an adequate public health response to the potential adverse health effects of legalization.