Coffee consumption and Blood pressure

ASH - American Society of Hypertension 2011

Coffee Okay for Well-Managed Hypertensives


By Todd Neale, Staff Writer, MedPage Today
Published: May 23, 2011
Reviewed by Zalman S. Agus, MD; Emeritus Professor
University of Pennsylvania School of Medicine and
Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner

In a meta-analysis of five trials, consuming 200 to 300 milligrams of caffeine -- the amount found in one-and-a-half to two cups of coffee -- produced a mean increase in blood pressure of 8.1/5.6 mm Hg, according to Esther Lopez-Garcia, PhD, of Autonoma University of Madrid.

The effect was observed within the first hour and sustained for up to three hours, she reported at the American Society of Hypertension meeting here.

Although meta-analyses of studies looking at the longer-term effects could not be conducted because of methodological differences, the bulk of the evidence pointed to a lack of an effect from coffee and caffeine intake on blood pressure and cardiovascular risk.

The association between coffee drinking and blood pressure has been well studied in normotensive individuals, with consistent findings of an acute increase in blood pressure after intake but no long-term risk of becoming hypertensive or having a cardiovascular event, according to Lopez-Garcia.

Some studies have even tied coffee drinking to a lower stroke risk, including a Swedish cohort study and an analysis of the Nurses' Health Study.

However, the relationship has not been studied as thoroughly in hypertensive individuals, in whom even a slight increase in blood pressure might be harmful.

In addition, Lopez-Garcia said that it is unknown whether coffee might reduce the effect of antihypertensive drug treatment and whether hypertensive individuals are able to develop a tolerance to caffeine like their normotensive counterparts.

Thus, she said, evidence is insufficient to guide medical advice regarding coffee and caffeine consumption in hypertensive individuals.

To explore the issue, Lopez-Garcia and her colleagues reviewed the literature and performed meta-analyses when possible.

In the meta-analysis of trials examining the acute effect of coffee and caffeine consumption, blood pressure was increased in the first three hours after intake, regardless of the duration of caffeine abstinence before the trial started and of the use of antihypertensive drugs.

Four other studies examined the longer-term effects of interventions involving coffee or caffeine intake. The two studies comparing coffee versus decaffeinated coffee found no longer-term effect on blood pressure up to eight weeks after the intervention.

Of two studies comparing coffee with a caffeine-free diet, however, one demonstrated a significant increase in systolic blood pressure in the coffee group (mean change 5.2 mm Hg). That came with an intervention consisting of drinking five cups of coffee a day.

There is not enough evidence to draw firm conclusions, Lopez-Garcia said, but the bulk of the evidence suggests that there is no longer-term effect on blood pressure from drinking coffee or caffeinated beverages.

A meta-analysis also was not possible for the five cohort studies -- with durations ranging from four to 25 years -- examining the relationship between habitual consumption of coffee and caffeinated beverages and cardiovascular risk.

Three studies found no association between habitual caffeine intake and risk of cardiovascular mortality.

Of two studies using stroke as an endpoint, one found a doubling in the risk (RR for the consumption of 20 ounces of coffee per day 2.1, 95% CI 1.2 to 3.7). The other failed to show a significant association.

Overall, the findings suggest that the relationship between coffee and caffeine consumption and blood pressure is similar in hypertensive and normotensive individuals, Lopez-Garcia said.

She said that one of the clinical implications of the findings is that the consumption of coffee or caffeinated beverages may alter blood pressure measurements in routine check-ups.

The findings also show that in hypertensive patients with well-controlled blood pressure, it may be safe to consume coffee, she added, but "for patients with uncontrolled blood pressure, moderation in coffee consumption is suggested."

The study was funded in part by an FIS research grant. Lopez-Garcia was supported by a Ramón y Cajal contract, and one of her co-authors was supported by a MAEC-AECID fellowship.

Lopez-Garcia reported that she had no conflicts of interest.