Excessive Coffee Consumption Could Spell Disaster for People with Hypertension

Hiroyasu Iso, MD, PhD, MPH

An analysis of data from more than 18,000 adults in Japan suggests consuming 2 cups of coffee or more per day was associated with a doubling in risk of cardiovascular death compared to non-drinkers among people with hypertension.

An analysis of the Japan Collaborative Cohort Study for Evaluation of Cancer Risk, data from the analysis suggest increase coffee consumption was associated with a 2-fold increase in cardiovascular mortality among those with grade 2-3 hypertension, but this association was not present among those with optimal blood pressure or grade 1 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 senior investigator Hiroyasu Iso, MD, PhD, MPH, director of the Institute for Global Health Policy Research, Bureau of International Health Cooperation, National Center for Global Health and Medicine and professor emeritus at Osaka University, in a statement. “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.”

An age-old question, countless studies have been conducted with the aim of understanding the impact of caffeine consumption on health and well-being. In the current study, Iso, along with a team of collaborators from Osaka University, sought to build on the existing research base by exploring the impacts of coffee and green tea consumption on cardiovascular mortality in people with severe hypertension. To do so, investigators designed the current study as an analysis of data from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC).

A nationwide, community-based prospective study, the JACC study enrolled patients aged 40-79 years from 1988-1990 from 45 communities in China. In total, the study enrolled 110,585 individuals. Limiting the cohort to those with measured blood pressure and full questionnaire data, investigators obtained data related a cohort of 18,609 individuals for inclusion in their current analyses. This cohort of 18,609 included 6574 men and 12035 women. The cohort had a median follow-up of 18.9 years.

For the purpose of analysis, investigators stratified participants into 4 blood pressure categories with these categories defined as optimal and normal blood pressure, high-normal blood pressure, grade 1 hypertension, and grade 2-3 hypertension. Of the 18,609 included in the study, 8322 had optimal and normal blood pressure,

During the follow-up period, 842 instances of cardiovascular death were recorded. Upon analysis, results suggested increased coffee consumption was associated with an increased risk of cardiovascular mortality among those with grade 2–3 hypertension, who had HRs of 0.98 (95% CI, 0.67-1.43) for less than 1 cup per day, 0.74 (95% CI, 0.37-1.46) for 1 cup per day, and 2.05 (95% CI, 1.17-3.59) compared to non-coffee drinkers. These associations were not observed for those classified as having optimal and normal blood pressure, high-normal blood pressure, and grade 1 hypertension, according to investigators. Additionally, results indicated green tea consumption was not associated with an increased risk of cardiovascular disease across any of the 4 blood pressure categories.

”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.”

This study, “Coffee and Green Tea Consumption and Cardiovascular Disease Mortality Among People With and Without Hypertension,” was published in the Journal of the American Heart Association.