Drinking two or more cups of coffee a day may double risk of death for those with severe hypertension

Findings from a recent study suggested that those with severe hypertension who drank two or more cups of coffee per day were twice as likely to die from heart complications than those with hypertension that did not drink coffee.

The study was published in the Journal of the American Heart Association and led by Hiroyasu Iso, MD, PhD, MPH, of the National Center for Global Health and Medicine in Tokyo, Japan. The study’s researchers sought to observe the effects that coffee and green tea had on the mortality of patients 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,” said Iso in a statement.

Included in the study were 18,609 participants from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC) aged 40 to 79, who had completed several questionaries on their lifestyle, diet, and medical history. Of the participants, 6,574 were men and 12,035 were women.

Researchers followed up with the patients almost 19 years after they enrolled in the JACC. Results suggested that drinking two or more cups of coffee a day doubled the risk of cardiovascular death in those with severe hypertension. Drinking only one cup of coffee a day, however, was not associated with increased risk for cardiovascular death, regardless of blood pressure levels. In addition, green tea consumption was not linked to increased risk of cardiovascular disease mortality.

“These findings may support the assertion that people with severe high blood pressure should avoid drinking excessive coffee,” said Iso. “Because people with severe hypertension are more susceptible to the effects of caffeine, caffeine’s harmful effects may outweigh its protective effects and may increase the risk of death.”

Authors concluded that the study’s results indicate a relationship between cardiovascular death, severe hypertension, and coffee consumption, but they did acknowledge limitations of the investigation. Future studies, according to researchers, should explore the cause-and-effect relationship between those with high blood pressure and coffee consumption.