Marijuana users have about a threefold risk of dying from hypertension, and the risk increases with each additional year of use, according to a National Health and Nutrition Examination Survey (NHANES) analysis.
The cardiovascular risk associated with marijuana use “may be greater than the cardiovascular risk already established for cigarette smoking,” report the authors, led by Barbara Yankey (Georgia State University, Atlanta).
“We are not disputing the possible medicinal benefits of standardized cannabis formulations; however, recreational use of marijuana should be approached with caution.”
The study was published online August 8, 2017 in the European Journal of Preventive Cardiology.
The researchers linked data from adults aged 20 and older who responded to questions about marijuana use on the 2005 NHANES to mortality data from the 2011 National Center for Health Statistics. The 1213 individuals (mean age 37.7 years at entry) in the cohort were followed for a total of 19,569 person-years.
Among all participants, 34% neither used marijuana or cigarettes, 21% used only marijuana, 20% used marijuana and smoked cigarettes, 16% used marijuana and were past smokers, 5% were past smokers, and 4% smoked only cigarettes. The average duration of marijuana use was 11.5 years and 10.1 years for cigarette smoking.
Compared with marijuana nonusers, marijuana users had an adjusted hazard ratio (HR) for death due to hypertension of 3.42 (95% CI 1.20–9.79).
The adjusted risk was greater than that for current cigarette smokers (HR 1.06; 95% CI 0.40–2.77), former smokers (1.33; 95% CI 0.57–3.10), alcohol users (HR 0.95; 95% CI 0.37–2.45), and those with a prior diagnosis of hypertension (HR 0.81; 95% CI 0.32–2.06) or CVD (HR 1.94; 95% CI 0.42–8.97).
For each year of marijuana use, the hazard ratio was 1.04 (95% CI 1.00–1.07). Death from hypertension included multiple causes such as primary hypertension and hypertensive renal disease.
There was no association between marijuana use and death from heart disease or cerebrovascular disease and no significant association between cigarette smoking and death from hypertension, heart disease, or cerebrovascular disease, most likely due to the small sample size, the researchers say.
“We found higher estimated cardiovascular risks associated with marijuana use than cigarette smoking,” Yankey said in a news release. “This indicates that marijuana use may carry even heavier consequences on the cardiovascular system than that already established for cigarette smoking. However, the number of smokers in our study was small, and this needs to be examined in a larger study.”
Another limitation of the study is how marijuana use was estimated. For example, it’s uncertain whether participants continued to smoke marijuana throughout the study period, the researchers note.
Nonetheless, the results point to a “possible risk of hypertension mortality from marijuana use. This is not surprising since marijuana is known to have a number of effects on the cardiovascular system,” Yankey said in the release.
Case reports have also detailed MI and stroke following marijuana use among normotensives and people without a CVD history.
“The relationship between marijuana use and cardiovascular mortality is understudied,” Yankey told theheart.org | Medscape Cardiology. “The current advance toward legalization of marijuana necessitates the study of the relationship between marijuana and cardiovascular health. If marijuana use really causes increased cardiovascular mortality, it’s important to take steps to protect the health of those who are likely to initiate or increase marijuana use because of its legalization,” Yankey said.
Commenting to theheart.org | Medscape Cardiology, addiction psychiatrist Dr Kevin P Hill (McLean Hospital, Belmont, MA, Harvard Medical School, Boston) said, “The bottom line is that these association studies raise questions that should be studied further in prospective studies.
“Now that we have 29 states and DC with medical cannabis and eight states and DC with legal cannabis, we have an opportunity to organize rigorous prospective studies to answer these questions about the health effects of cannabis more effectively than we have before,” he added.