Hypertension and Heavy Coffee Consumption a Bad Combo, Study Finds

Most of the literature shows coffee to be health friendly, but it makes sense for patients with high BP to cut back, an expert says.

Hypertension and Heavy Coffee Consumption a Bad Combo, Study Finds

Drinking multiple cups of coffee a day could increase the risk of CVD mortality in people with severe hypertension, according to an analysis of a Japanese population.

The increased risk was only seen in those whose blood pressure put them into the category of grade 2-3 hypertension (160 to > 180 mm Hg systolic or 100 to > 110 mm Hg diastolic, based on the 2018 European guidelines) and who self-reported drinking two or more cups of coffee each day.

The researchers, led by Masayuki Teramoto, MD (Osaka University Graduate School of Medicine, Japan), note that for most people in the general population, harmful effects of caffeine such as transient BP elevation are likely offset by demonstrated protective effects such as lowering serum cholesterol levels and improving endothelial function. However, “caffeine’s harmful effects may outweigh its protective effects and increase the risk of mortality in people with severe hypertension.”

Commenting for TCTMD, Christopher Gardner, PhD (Stanford University School of Medicine, CA), said the literature over the last 20 years has been overwhelmingly positive in demonstrating health benefits and lack of harm of coffee consumption. That being said, he acknowledged that the new data do give pause.

“I don’t see any reason not to take this fairly seriously,” said Gardner, who is chair of the American Heart Association’s nutrition committee. Yet the data don’t suggest that people with serious hypertension need to forgo the java entirely or lose their morning ritual: they just need to cut back to a single cup per day or think about incorporating tea or decaf. This small change is “not much of an ask” for someone with a serious health condition like severe hypertension, he said.

That being said, Gardner also pointed out some flaws in the study that need addressing. Specifically, the increased CVD mortality risk associated with two or more cups of coffee per day and grade 2-3 hypertension was applicable to just 19 out of 18,000 people in the study, a finding that would have been masked had the researchers not gone to such great lengths to categorize people by their coffee consumption level and hypertension grade. Doing so also revealed wide confidence intervals, which puts the actual increased risk in the high-BP heavy coffee drinkers potentially as low as 7%.

In light of those issues impeding interpretation of the study, Gardner said it might make sense for others like the Nurses’ Health Study or the European Prospective Investigation into Cancer and Nutrition (EPIC), for example, to replicate the Japanese analysis in larger, more diverse populations to see if the association sticks.

No Impact of Coffee or Tea at Lower BP Levels

For the study, published online last week in the Journal of the American Heart Association, Teramoto and colleagues examined data on 18,609 men and women aged 40 to 79 years who participated in the Japan Collaborative Cohort Study for Evaluation of Cancer Risk. These individuals completed a lifestyle, diet, and medical history questionnaire and underwent health examinations beginning in 1988-1990.

Participants were grouped into four BP categories: optimal and normal (< 130 mm Hg systolic/< 85 mm Hg diastolic), high-normal (130-139 mm Hg systolic or 85-89 mm Hg diastolic), grade 1 (140-159 mm Hg systolic or 90-99 mm Hg diastolic), grade 2 (160-179 mm Hg systolic or 100-109 mm Hg diastolic), and grade 3 (≥ 180 mm Hg systolic or ≥ 110 mm Hg diastolic). Grades 2 and 3 were combined into one cohort due to low numbers.

Over nearly 19 years of follow-up, 842 deaths occurred. In those with grade 2-3 hypertension, mortality was not increased with less than one cup of coffee per day compared with no coffee (HR 0.98; 95% CI 0.67-1.43) or with one cup per day (HR 0.74; 95% CI 0.37-1.46), but it was increased with two or more cups were day (HR 2.05; 95% CI 1.17-3.59). Looking across the spectrum of optimal and normal, high-normal BP, and grade 1 hypertension, no differences were seen in CVD mortality by coffee consumption level.

Green tea, even at five to six cups per day, showed no impact on mortality at any BP category.

For Gardner, another factor that needs to be illuminated to understand any potential connection between coffee consumption and mortality is how much caffeine people are drinking and what they consider “coffee” to be. He noted that while older coffee studies consisted of people who were drinking primarily black coffee, today’s coffee lovers may have more sugar and calories in their cup than actual coffee.

“Different populations [can] mean different types of coffee . . . and that goes for [assuming] coffee is beneficial, too, which is something I’m a little wary of people saying,” Gardner added.

Sources
Disclosures
  • Teramoto and Gardner report no relevant conflicts of interest.

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