Clinical Context

Among the general population, coffee drinking may lower risk for incident hypertension (HTN) and mortality. However, among people with HTN, it may increase blood pressure (BP) in the short‐term. An experimental study suggested that the preventive effect of caffeinated coffee drinking depends on BP level and applies only to people without severe HTN.

Drinking caffeinated green tea lowers BP among people with pre-HTN and stage 1 HTN. Evidence suggests that it also reduces cardiovascular disease (CVD) and all-cause mortality among those with CVD and the general population.

Study Synopsis and Perspective

Individuals with severe HTN who drink 2 or more cups of coffee a day have double the long-term risk for death from CVD compared with those who do not consume coffee, suggest data from a population-based cohort study conducted in Japan.

The analysis explored whether the possible cardioprotective effects of coffee and green tea intake seen in epidemiologic studies apply regardless of BP, across different degrees of HTN severity, lead author Masayuki Teramoto, MD, MPH, from the University of California, San Francisco, told theheart.org | Medscape Cardiology.

Dr Teramoto said that he was surprised that “heavy” coffee consumption (at least 2 cups daily) was associated with increased CVD mortality among people with severe HTN but not those with normal BP or grade 1 HTN.

“In contrast,” he said, “green tea consumption was not associated with an increased risk of CVD mortality across all [BP] categories” in the analysis, which was based on more than 18,000 men and women in Japan who were followed for a median of 19 years.

Previous research has shown that greater coffee intake may cut the risk for incident HTN and mortality among the general population, but it can also increase BP over the short term among persons with HTN, Dr Teramoto noted. The protective effects, therefore, appear to depend on the individual’s BP.

“Because hypertensives are more susceptible to the effects of caffeine,” he said, “caffeine’s harmful effects may outweigh its protective effects and increase the risk of mortality in persons with severe [HTN].”

Dr Teramoto is lead author on the study, published online December 21 in the Journal of the American Heart Association.

The analysis was based on data from 18,609 participants (including 65% women) in the Japan Collaborative Cohort Study for Evaluation of Cancer Risk study, which enrolled people aged 40 to 75 years living throughout Japan. The participants completed self-reported questionnaires on their medical history, diet, and lifestyle.

Their baseline BP was classified into 5 categories: optimal and normal (<130/85 mm Hg); high normal (130-139/85-89 mm Hg); grade 1 HTN (140-159/90-99 mm Hg); grade 2 HTN (160-179/100-109 mm Hg), and grade 3 HTN (>180/110 mm Hg).

Because of the low percentage of participants with grade 3 HTN, the grade 2 and 3 categories were combined into “severe” HTN.

Participants were asked in a survey about the frequency and amount of coffee and green tea they consumed and were classified into 4 levels of daily coffee consumption (occasionally or none, less than 1 cup, 1 cup, or 2 or more cups) and 6 levels of daily green tea consumption (occasionally or none, less than 1 cup, 1 to 2 cups, 3 to 4 cups, 5 to 6 cups, or 7 or more cups).

A total of 842 participants died during a median follow-up of 19 years.

Greater coffee consumption was associated with increased risk for CVD mortality only among participants with grade 2 to 3 HTN at an intake of 2 or more cups per day. The adjusted hazard ratio was 2.05 (95% CI, 1.17-3.59) compared with participants with severe HTN who did not drink coffee.

No associations between coffee consumption and CVD death were observed among participants with optimal/normal or high-normal BP or with grade 1 HTN.

Green tea consumption was not associated with an increased risk for CVD across any BP categories. However, among people with grade 2 to 3 HTN, frequent green tea consumption was associated with a lower total cholesterol level.

“These are very interesting findings, because for the last decade or more, studies like these. . .have very consistently concluded there are benefits to both types of beverages,” American Heart Association Nutrition Committee chair Christopher Gardner, PhD, told theheart.org | Medscape Cardiology.

“What was unique about this study was the extra step of looking separately at 4 ranges of blood pressure.”

But he also expressed some concerns and caveats. For example, there were numerous participant subcategories by both BP and coffee consumption, such that “the rate of CVD mortality in the group of heavy coffee drinkers among participants with severe [HTN] was determined from just 19 events.” That makes up only 2% of CVD deaths. “This limits how robust the findings are.”

Also, the hazard ratio CIs for risk in patients with severe HTN consuming at least 2 cups coffee daily were wide. The 2-fold increased risk “could have been as little as a 17% increase in risk. . .or as much as a 3-fold risk,” Dr Gardner said.

Dr Gardner also noted the study’s failure to account for additives to coffee and tea drinks. For example, black coffee and a mocha frappe or cappuccino “might both qualify as coffee, but the latter is a sugar and saturated fat delivery vehicle.” Similarly, green tea and bubble tea both potentially qualify as tea, “but the latter is more of a tea-flavored beverage with sugar and dairy and other additives.”

Omission of this information raises concern, he said, that the study may encourage consumers with no or mild HTN to increase their consumption of potentially harmful coffee-like and tea-like beverages.

There are no daily nutritional requirements for coffee, tea, or caffeine, Dr Gardner said, “suggesting that adults with severe [HTN who] limit their coffee to 1 cup per day would not [experience] any nutrient deficiencies.”

The risk-benefit ratio for coffee intake and CVD mortality implied by the study “probably falls in line with recommending they limit their coffee consumption to less than 2 cups per day, until more results are available.”

The Japan Collaborative Cohort Study for Evaluation of Cancer Risk study 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 National Cancer Center Research and Development Fund; and the Japan Society for the Promotion of Science. The authors and Dr Gardner have disclosed no relevant financial relationships.

J Am Heart Assoc. Published online December 21, 2022.^[1]

Clinical Implications

• Heavy coffee drinking was associated with increased risk for CVD mortality among people with severe HTN, but not people without HTN or grade 1 HTN; green tea was not associated with increased CVD mortality risk in any BP categories.
• Caffeine’s harmful effects may outweigh coffee’s protective effects and increase mortality risk in people with severe HTN, who are more susceptible to caffeine’s effects.
• Implications for the Health Care Team: Members of the healthcare team should provide education on the possible effects of heavy coffee drinking, as the study findings may support the assertion that people with severe HTN should avoid it.

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