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A pair of new preliminary studies have found that older adults who use marijuana every day but don't smoke tobacco appear to be significantly more likely to suffer serious cardiovascular emergencies including heart attacks and strokes.

The first study, presented this week by the American Heart Association Scientific Sessions in Philadelphia but not yet published, followed about 157,000 patients with a median age of 54 over almost four years. Participants self-reported their marijuana use through surveys over that period.

A whopping 34 percent of respondents who reported daily marijuana use had an increased risk of developing heart failure compared to those who never used the drug, the researchers found.

"The latest research about cannabis use indicates that smoking and inhaling cannabis increases concentrations of blood carboxyhemoglobin (carbon monoxide, a poisonous gas), tar (partly burned combustible matter) similar to the effects of inhaling a tobacco cigarette, both of which have been linked to heart muscle disease, chest pain, heart rhythm disturbances, heart attacks and other serious conditions," said Robert Page II, professor of clinical pharmacy at the University of Colorado who was not involved in the studies, in a statement.

The second study — which examined data from the 2019 National Inpatient Sample, a huge nationwide database of hospitalizations — found that out of the 28,535 adult cannabis users with existing risk factors like high blood pressure, high cholesterol, or diabetes, 20 percent were at an increased risk of having a major heart or brain event while hospitalized compared to those not using cannabis. And 13.9 percent of cannabis users with these risk factors did have a major adverse heart and brain event compared to those who didn't use the drug.

It's a pertinent topic, with the number of Americans smoking cannabis or using edibles growing significantly over the last eight years.

"Since 2015, cannabis use in the US has almost doubled, and it is increasing in older adults, therefore, understanding the potential increased cardiovascular risk from cannabis use is important," said lead study author Avilash Mondal, resident physician at Nazareth Hospital in Philadelphia, in the statement. "What is unique about our study is that patients who were using tobacco were excluded because cannabis and tobacco are sometimes used together, therefore, we were able to specifically examine cannabis use and cardiovascular outcomes."

As a result, Mondal said that "we must be mindful about major heart and stroke events in older adults with cannabis use disorder," while asking healthcare professionals to "include the question, 'Are you using cannabis?' when taking a patient’s history."

The research is an ominous hint that there could be medical downsides to cannabis use in an era of rapidly spreading legalization, but it comes with some important caveats.

For one, the data the researchers relied on didn't specify whether marijuana was inhaled or consumed via edibles, something that could "influence cardiovascular outcomes," per the statement.

Then there's the fact that researchers were relying on a large database which may have coding errors. Not every health institution agrees on a common definition of marijuana addiction or use disorder, which could also undermine the results.

In other words, scientists still have a lot of work to do before we can get a more detailed picture — but it's clear that some public health researchers are concerned.

"Together with the results of these two research studies, the cardiovascular risks of cannabis use are becoming clearer and should be carefully considered and monitored by health care professionals and the public," said Robert Page II in the statement.

More on marijuana: Scientists Find That Weed Is Leaving Heavy Metals in Your Body

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