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


Research Highlights:

  • Drinking two or more cups of coffee a 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.

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

Embargoed until 4:00 AM CT/5:00 AM ET, Wednesday, December 21, 2022

(NewMediaWire) – Dec 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 among people with hypertension pressure not considered severe, according to research published today in Journal of the American Heart Associationan open access, peer-reviewed journal of the American Heart Association.

In contrast, the study found that a cup of coffee and daily consumption of green tea did not increase the risk of death related to cardiovascular disease in any measurement 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 research has found that drinking a cup of coffee a day may help heart attack survivors by lowering their risk of death after a heart attack and may prevent heart attacks or strokes in healthy individuals. Additionally, separate studies have suggested that drinking coffee regularly may reduce the risk of developing chronic diseases such as type 2 diabetes and some cancers; can help control appetite; may help lower the risk of depression or increase alertness, although it’s not clear whether this effect is from the caffeine or something else in the coffee. On the harmful side, too much coffee can raise blood pressure and cause anxiety, heart palpitations, and difficulty sleeping.

“Our study aimed to determine whether the known protective effect of coffee also applies to individuals with varying degrees of hypertension; and also examined the effects of green tea in the same population,” explained senior study author Hiroyasu Iso, MD, Ph.D. ., MPH, 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 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 high blood pressure, occurs when the force of blood against blood vessel walls is consistently too high, causing the heart to work harder to pump blood. It is measured in millimeters of mercury (mm Hg). Current American Heart Association and American College of Cardiology blood pressure guidelines 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 mm Hg); and grade 3 (greater than 180/110 mm Hg). Grade 2 and 3 blood pressure measurements were considered severe hypertension in this study.

Study participants included more than 6,570 men and more than 12,000 women, ages 40 to 79 at baseline. They were selected from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk, a large prospective study conducted between 1988 and 1990 with adults living in 45 Japanese communities. Participants provided data through health screenings and self-administered questionnaires assessing lifestyle, diet, and medical history.

During nearly 19 years of follow-up (through 2009), 842 deaths related to cardiovascular disease were documented. Data analysis for 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 didn’t drink coffee.

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

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

“These findings may support the claim that people with severe hypertension should avoid excessive coffee drinking,” said Iso. “As people with severe hypertension are more susceptible to the effects of caffeine, the harmful effects of caffeine may outweigh its protective effects and 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 why coffee consumption alone was associated with an increased risk of death in people with severe high blood pressure, despite both green tea and coffee containing caffeine.

The survey has several limitations: coffee and tea consumption was self-reported; blood pressure was measured at a single point, which did not take changes over time into account; and the observational nature of the study failed to establish a direct cause-and-effect connection between coffee consumption and the risk of cardiovascular disease 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 on people with high blood pressure and to confirm the effects of coffee and green tea consumption in other countries.

Co-authors are Masayuki Teramoto, MD, MPH; Kazumasa Yamagishi, MD, Ph.D.; Isao Muraki, MD, Ph.D.; and Akiko Tamakoshi, MD, Ph.D. The authors’ statements are listed in the manuscript.

The Japan Collaborative Cancer Risk Assessment Cohort Study was funded by the Ministry of Education, Culture, Sports, Science and Technology of Japan; Ministry of Health, Labor and Welfare, Health and Occupational Sciences, Japan; the National Cancer Center Research and Development Fund; and the Japanese 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 Association’s policy or position. The Association makes no representations or warranties as to their accuracy or reliability. The Association receives funding primarily 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 the content of science. Revenues from pharmaceutical and biotechnology companies, device manufacturers and health insurance providers and general financial information for the Association are available here.

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