Drinking two or more cups of coffee a day could put people with severely high blood pressure more at risk of suffering a stroke or heart attack.

The latest study findings showed regular intake of caffeinated coffee in volumes of two or more cups could double the risk of hypertensive patients dying from a heart attack, stroke and other cardiovascular diseases.

Interestingly, the same results were not found among those who drank green tea or just one cup of coffee daily.

According to the researchers behind the study published in the Journal of the American Heart Association Wednesday, their main goal was to examine the impacts of coffee and green tea consumption on cardiovascular disease (CVD) mortality among people with severe hypertension.

“Our study aimed to determine whether the known protective effect of coffee also applies to individuals with different degrees of hypertension and also examined the effects of green tea in the same population,” senior study author Dr. Hiroyasu said in a news release.

For the study, the team examined data from 18,609 participants aged 40 to 79. The participants were asked to complete a lifestyle, diet and medical history questionnaire. They also had health examinations.

“Heavy coffee consumption was associated with an increased risk of CVD mortality among people with severe hypertension, but not people without hypertension and with grade 1 hypertension. In contrast, green tea consumption was not associated with an increased risk of CVD mortality across all categories of blood pressure (BP),” the team wrote in their conclusion.

Prior research suggested that people who had a heart attack but drank one cup of caffeinated coffee daily could lower their death risk. This was also believed to help prevent heart attacks and strokes in healthy adults. However, other studies showed that too much coffee could increase blood pressure and even cause heart palpitations and anxiety, according to the American Heart Association.

Both coffee and tea contain caffeine but in varying levels. An 8-ounce cup of green or black tea contains 30 to 50 mg caffeine. On the other hand, the same volume of coffee contains 80 to 100 mg of caffeine, as per the Food and Drug Administration.

Iso, the director of the Institute for Global Health Policy Research at the National Center for Global Health and Medicine in Tokyo, pointed out that the study findings should encourage people with severe hypertension to avoid drinking excessive coffee.

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