The study investigated the impact of coffee consumption on participants with untreated cases of mild hypertension.
The research is being presented at the European Society of Cardiology (ESC) Congress by study author Dr. Lucio Mos, a cardiologist at Hospital of San Daniele del Friuli in Udine, Italy.
"There is controversy surrounding the long-term cardiovascular and metabolic effects of coffee consumption in patients with hypertension," Dr. Mos reports. "Our study was designed to evaluate whether coffee drinking had an effect on the risk of cardiovascular events, and if the association was mediated by effects on blood pressure and glucose metabolism."
Such is coffee's popularity around the world, there is a wide variety of research that has been conducted on the effects of its consumption. Recently, Medical News Today has reported on studies that have suggested coffee could improve survival in colon cancer patients and reduce the risk of erectile dysfunction.
However, the majority of studies of coffee that MNT has looked at in recent months have linked coffee consumption with positive health outcomes. The new study differs in this respect.
The researchers investigated the coffee consumption habits of 1,201 non-diabetic patients aged 18-45 years participating in the prospective HARVEST2 study. Each participant had stage 1 hypertension (systolic blood pressure of 140-159 mm/Hg and/or diastolic blood pressure of 90-99 mm/Hg) but were not receiving treatment for it.
Coffee consumption was defined by the amount of cups of caffeine-containing coffee participants drank every day. Non-drinkers reported no cups a day, moderate drinkers consumed between one and three cups daily and heavy coffee drinkers consumed four or more per day.
Among the participants of the study, 26.3% did not drink coffee, 62.7% were moderate coffee drinkers and 10% were heavy coffee drinkers.
Young adults with mild hypertension 'should keep consumption to a minimum'
Type 2 diabetes is frequently known to develop in patients with hypertension at a later stage, and so the researchers investigated how coffee drinking influenced the risk of developing prediabetes over time, following the participants for 12.5 years.
- More than 400 billion cups of coffee are consumed every year worldwide
- Coffee is one of the most common sources of antioxidants in the American diet
- Some studies have suggested coffee could help protect against type 2 diabetes, Parkinson's disease and cancer.
How quickly the participants metabolized caffeine - determined by the CYP1A2 genotype - influenced this risk. Only in heavy coffee drinkers who metabolized caffeine slowly did the risk of prediabetes increase significantly.
"Slow caffeine metabolizers have longer exposure to the detrimental effects of caffeine on glucose metabolism," Dr. Mos explains. "The risk is even greater if they are overweight or obese, and if they are heavy coffee drinkers. Thus, the effect of coffee on prediabetes depends on the amount of daily coffee intake and genetic background."
During the study's follow-up period, a total of 60 cardiovascular events were observed, with the majority of these (80%) being heart attacks.
Both heavy and moderate consumption of coffee were independent predictors of cardiovascular events, although these risks were reduced when including hypertension development and future prediabetes in the analysis, after which the only significant relationship was with heavy coffee consumption.
Dr. Mos concludes that the study shows coffee use is linearly associated with increased risk of cardiovascular events in young adults with mild hypertension:
"This relationship seems to be at least partially mediated by the long-term effect of coffee on blood pressure and glucose metabolism. These patients should be aware that coffee consumption may increase their risk of developing more severe hypertension and diabetes in later life and should keep consumption to a minimum."
Last year, MNT reported on a meta-analysis that found genetic reasons for why caffeine has different effects on different people, potentially explaining certain people's coffee drinking habits.