Two coffees a day doubles cardio mortality in people with severe hypertension

Consumption of two or more cups of coffee a day doubles the risk of death from cardiovascular disease among people with severe high blood pressure (160/100 mm Hg or higher) compared with people with lower blood pressure.

Researchers reported these findings on Dec. 21, 2022 in the Journal of the American Heart Association.

They also reported that one cup of coffee and daily green tea consumption did not raise the risk of death related to cardiovascular disease at any blood pressure measurement.

“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,” explained the study’s senior author Hiroyasu Iso, M.D., Ph.D., M.P.H., director of the Institute for Global Health Policy Research, Bureau of International Health Cooperation, National Center for Global Health and Medicine in Tokyo, Japan, and professor emeritus at Osaka University. “To the best of our knowledge, this is the first study to find an association between drinking 2 or more cups of coffee daily and cardiovascular disease mortality among people with severe hypertension.”

The investigators classified five categories of blood pressure — optimal and normal (less than 130/85 mm Hg), high normal (130-139/85-89 mm Hg), grade 1 hypertension (140-159/90-99 mm Hg), grade 2 (160-179/100-109 mm Hg), and grade 3 (higher than 180/110 mm Hg).

Blood pressure in grades 2 and 3 were, in this study, deemed to be “severe hypertension.”

In the JACC (Japan Collaborative Cohort Study for Evaluation of Cancer Risk), 18,609 subjects (6,574 male and 12,035 female) aged 40 to 79 years were enrolled. At baseline, subjects provided data through health examinations and self-administered questionnaires assessing lifestyle, diet and medical history. They were tracked for 18.9 years, until 2009.

The researchers reported that consumption of two or more cups of coffee a day was associated with double the risk of cardiovascular disease-related mortality among subjects whose blood pressure was 160/100 mm Hg or higher compared to subjects who drank no coffee.

Consumption of one cup of coffee a day did not appear to raise the risk of death from cardiovascular disease in any blood pressure group. Likewise, green tea consumption did not increase the risk of cardiovascular disease mortality in any blood pressure group.

“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.”

The authors concluded, “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.”