Although the type of stroke studied, aneurysmal subarachnoid hemorrhage (aSAH), comprises only about 5% of all stroke cases, it causes neurological disability in about two-thirds of patients and eventually kills about 40%.
A leading cause of this disability or death following an aSAH stroke is DCI, which can develop within 14 days of the initial stroke. "Given the popularization of cannabis use in the United States, it is essential to continue evaluating the associated risks and benefits," Dr. Michael T. Lawton of Barrow Neurological Institute, in Phoenix, and colleagues write in Stroke.
The authors reviewed records, including routine urine toxicology, of all 1,014 patients treated for aSAH at their center from 2007 to 2019, 367 (36.2%) of whom developed DCI.
Of the entire cohort, 46 patients (4.5%) were positive for cannabis. The initial toxicology screen indicated cannabis use within the previous three to 30 days, depending on the patient's amount of use.
The incidence of DCI was significantly higher in cannabis users than in the other patients (52.2% vs. 35.4%, P=0.03). A propensity-score analysis showed that patients who tested positive for cannabis had 2.7 times greater odds of developing DCI (P=0.003).
"Aneurysm rupture is not as common as cancers, heart disease, and other conditions, but is not rare," Dr. Lawton told Reuters Health by email. "This research matters because it has identified a previously unrecognized danger associated with cannabis use that users should consider in deciding whether to continue."
The authors note that their study's statistical power was limited by a lower-than-expected positive-screening rate for cannabis.
Dr. Lawton said that previous studies have reported rates of cannabis use as high as 25% in aSAH patients. "The rate in the present study may be lower because of an older patient population that is encountered in the greater Phoenix area, thus, less marijuana use," he explained.
In accompanying editorial, Drs. Feras Akbik and Ofer Sadan of the Department of Neurology and Neurosurgery at Emory University School of Medicine, in Atlanta, point to a physiological mechanism by which the tetrahydrocannabinol in cannabis might affect both cardiac vasculature and cerebrovasculature.
However, they also highlight the mixed findings of previous studies that looked for an association between cannabis use and increased cardio/cerebrovascular complications, including DCI.
Dr. George Howard of the University of Alabama at Birmingham, who studies cardiovascular and cerebrovascular risk factors and was not involved in the new study, said, "Cannabis is a real challenge from a research standpoint," especially determining use. If you even ask about cannabis, he said, many people will immediately drop out of a study.
Though SAH strokes are rare, he added, they're dangerous and "the people who have them are in deep trouble."
There is weak, but growing, evidence that cannabis increases stroke risk, Dr. Howard told Reuters Health by phone, and there's "probably an association" with atrial fibrillation also.
The researchers' use of drug-screen data was unusual and effective, he said. "Marijuana is hard to study, and this is a cool study, because of that tox screen."
Dr. Howard, a biostatistician, did criticize the authors' use of 18 factors in the study's propensity-score analysis, given the small number of cannabis users. "Having that many predictors is kind of a no-no."
He also cautioned, "There's a lot of things that travel with marijuana," especially tobacco and other drugs. Still, Dr. Howard concluded, "This paper is a big deal."
SOURCE: https://bit.ly/3AcIX4A Stroke, online January 5, 2022.
By Scott Baltic
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