HypeWatch: Researcher Claims Pot-Stroke Link on Limited Data

Conclusion based on analysis of 64 cases, no controls.

http://www.medpagetoday.com/Cardiology/Strokes/50109

A series of published case reports on 64 patients suggests that marijuana smoking may contribute to stroke risk in young and middle-age adults, a researcher asserted, although the reports were often incomplete and lacked controls.

Writing in the American Heart Association journal Stroke, Daniel Hackam, MD, of Western University in London, Ontario, summarized findings on the 64 cases, which ranged in age from 16 to 63, of which 52 appeared to feature a temporal association between marijuana smoking and ischemic stroke.

Also, in only half the cases were concomitant stroke risk factors identified in the reports, and 13 patients suffered recurrent strokes after re-exposure to marijuana, Hackam found. He argued that these went a considerable way toward fulfilling criteria in the so-called Naranjo probability scale for judging drug-related causality in adverse events.

“Given broad exposure to cannabis in the general population, it is striking that more strokes do not occur among cannabis users,” wrote Hackam, who has published extensively on cardiovascular risk factors. He speculated that frequency and intensity of marijuana smoking, the overall dose, genetic factors, and “coingestants” could play a role.

Although Hackam acknowledged that the study design could not prove causality — only “a prospective epidemiological study” could do that, he wrote — he nevertheless went on to imply that the relationship was indeed causal.

“It seems clear that physiological, clinical, and epidemiological data converge on an increased stroke risk from cannabis exposure,” Hackam concluded. “Heightened clinician awareness of this association, particularly in the treatment of young adults, is necessary for preventing recurrent events from future re-exposure to cannabis.”

Yet Hackam’s paper — published as a “Brief Report” — listed no limitations of the analysis, which was strictly observational, based on case descriptions from 33 separate groups with varied reporting styles.

All the reports included in the analysis indicated which vessel or brain region was affected, but for 19 of the patients other causes of stroke were not excluded, and data on other risk factors were missing for 23 patients.

Of the 13 with recurrent stroke, the reports indicated that all but one either had concomitant risk factors or their possible presence was unknown.

Hackam’s suggestion of causality also contradicts findings from a case-control study conducted in Baltimore reported last year — not cited in Hackam’s references — which found no difference in marijuana habits between stroke patients 14 to 49 years old and matched controls.

That there might be a connection is not wholly implausible. A French epidemiological survey, reported last year, found an association between marijuana use and cardiovascular complications in young adults, and an earlier case-control study in New Zealand had found that marijuana smoking was twice as common in middle-age stroke victims versus controls.

But the association seen in the New Zealand study disappeared when the researchers controlled for tobacco use, and the sample size was far smaller than in the Baltimore study.

From the American Heart Association

 

 

 

Filed under: General Problems