Drinking 2 or more cups of coffee a day may double the risk of cardiac death in people with severe hypertension.

Research Highlights:

  • Drinking two or more cups of coffee per day was associated with twice the risk of death from cardiovascular disease among people with severe hypertension compared with non-coffee drinkers, in a study of more than 18,600 men and women in Japan.

  • Drinking just one cup of coffee a day was not associated with an increased risk of death from cardiovascular disease at any blood pressure level.

  • By contrast, drinking green tea was not associated with an increased risk of cardiovascular disease-related death at any blood pressure level, even though both coffee and tea contain caffeine.

Embargoed until 4 am CT/5 am ET on Wednesday, December 21, 2022

(NewMediaWire) – December 21, 2022 – DALLAS Drinking two or more cups of coffee a day may double the risk of death from cardiovascular disease among people with severe high blood pressure (160/100 mm Hg or higher), but not people with high blood pressure not considered serious, according to research published today in the Journal of the American Heart Associationan open access peer-reviewed journal of the American Heart Association.

In contrast, the study found that a daily cup of coffee and green tea consumption did not increase the risk of cardiovascular disease-related death by any measure of blood pressure, even though both beverages contain caffeine. According to the FDA, an 8-ounce cup of green or black tea has 30 to 50 milligrams of caffeine, and an 8-ounce cup of coffee has about 80 to 100 milligrams.

previous investigation found that drinking a cup of coffee a day can help heart attack survivors by reducing the risk of death after a heart attack and can prevent heart attacks or strokes in healthy people. Additionally, separate studies have suggested that drinking coffee regularly may reduce the risk of developing chronic diseases, such as type 2 diabetes and some types of cancer; can help control appetite; it may help reduce the risk of depression or increase alertness, although it’s not clear if this effect is due to the caffeine or something else in the coffee. On the harmful side, too much coffee can raise your blood pressure and lead to anxiety, heart palpitations, and trouble sleeping.

“Our study aimed to determine whether the known protective effect of coffee also applies to people with different degrees of hypertension, and also examined the effects of green tea in the same population,” explained study lead author Hiroyasu Iso, MD. , Ph.D. ., MPH, director of the Institute for Global Health Policy Research, Office for International Health Cooperation, National Center for Global Health and Medicine in Tokyo, Japan, and professor emeritus at Osaka University. “To our knowledge, this is the first study to find an association between drinking 2 or more cups of coffee per day and cardiovascular disease mortality among people with severe hypertension.”

High blood pressure, also known as hypertension, occurs when the force of the blood pushing against the walls of the blood vessels is constantly too high, making the heart work harder to pump blood. It is measured in millimeters of mercury (mm Hg). Current blood pressure guidelines from the American Heart Association and the American College of Cardiology classify hypertension as a blood pressure reading of 130/80 mm Hg or higher.

The blood pressure criteria for this study are slightly different from the ACC/AHA guidelines. The researchers classified blood pressure into five categories: 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 mmHg); and grade 3 (greater than 180/110 mm Hg). Blood pressure measurements at grades 2 and 3 were considered severe hypertension in this study.

Study participants included more than 6,570 men and more than 12,000 women, aged 40 to 79 years at the start of the research. They were selected from the Japan Collaborative Cohort Study for Cancer Risk Assessment, a large prospective study established between 1988 and 1990 of adults living in 45 Japanese communities. Participants provided data through health exams and self-administered questionnaires that assessed lifestyle, diet, and medical history.

During nearly 19 years of follow-up (through 2009), 842 cardiovascular disease-related deaths were documented. Analysis of data from all participants found:

  • Drinking two or more cups of coffee a day was associated with twice the risk of death from cardiovascular disease in people whose blood pressure was 160/100 mm Hg or higher compared with those who did not drink coffee.

  • Drinking a cup of coffee a day was not associated with an increased risk of death from cardiovascular disease in any of the blood pressure categories.

  • Green tea consumption was not associated with an increased risk of cardiovascular disease mortality in any category of blood pressure.

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

The study found that people with more frequent coffee consumption were more likely to be younger, current smokers, current drinkers, eat fewer vegetables, and have higher total cholesterol levels and lower systolic blood pressure (top number) regardless of blood pressure category.

The benefits of green tea can be explained by the presence of polyphenols, which are micronutrients with healthy antioxidant and anti-inflammatory properties found in plants. The researchers noted that polyphenols may be part of the reason that only coffee consumption was associated with an increased risk of death in people with severe high blood pressure despite the fact that both green tea and coffee contain caffeine.

The research has several limitations: coffee and tea consumption was self-reported; blood pressure was measured at a single point, which did not account for changes over time; and the observational nature of the study was unable to establish a direct cause-and-effect connection between coffee consumption and cardiovascular disease risk among people with severe high blood pressure.

More studies are needed, the researchers said, to learn more about the effects of coffee and green tea consumption in people with high blood pressure and to confirm the effects of coffee and green tea consumption in other countries.

Coauthors are Masayuki Teramoto, MD, MPH; Kazumasa Yamagishi, M.D., Ph.D.; Isao Muraki, M.D., Ph.D.; and Akiko Tamakoshi, MD, Ph.D. Author statements are listed in the manuscript.

The Japan Collaborative Cohort Study for Cancer Risk Assessment was funded by the Ministry of Education, Culture, Sports, Science and Technology of Japan; the Ministry of Health, Labor and Welfare, Health and Labor Sciences, Japan; the Research and Development Fund of the National Cancer Center; and the Japan Society for the Promotion of Science.

Studies published in the scientific journals of the American Heart Association are peer reviewed. Statements and conclusions in each manuscript are solely those of the study authors and do not necessarily reflect the policy or position of the Association. The Association does not represent or guarantee its accuracy or reliability. The Association receives funding mainly from individuals; foundations and corporations (including pharmaceuticals, device manufacturers, and other companies) also make donations and fund specific Association programs and events. The Association has strict policies to prevent these relationships from influencing scientific content. Revenues from pharmaceutical and biotech companies, device manufacturers and health insurance providers and general financial information from the Association are available here.

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The American Heart Association is a relentless force for a world of longer, healthier lives. We are dedicated to ensuring equitable health in all communities. Through collaboration with numerous organizations and with the support of millions of volunteers, we fund innovative research, advocate for public health, and share life-saving resources. The Dallas-based organization has been a leading source of health information for nearly a century. Connect with us at heart.org, Facebook, Twitter or by calling 1-800-AHA-USA1.

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