The effect of chronic coffee drinking on blood pressure - A meta-analysis of controlled clinical trials

We sought to assess the effect of coffee consumption on blood pressure in h umans, Our data sources included a MEDLINE search of the literature publish ed before December 1997, bibliography review, and expert consultation, We s elected controlled trials in which coffee consumption was the only differen ce between the intervention and control groups, mean blood pressure change was reported for each group or period, and treatment lasted for >24 hours. Of 36 studies initially identified, 11 (522 participants) met these inclusi on criteria. Information on sample size, study design, participant characte ristics (gender, race, age, baseline blood pressure, and antihypertensive m edications), and treatment results were abstracted by 3 reviewers using a s tandardized protocol. Treatment effect of coffee consumption on blood press ure was estimated with the use of a random-effects model. In the 11 trials, median duration was 56 days (range, 14 to 79 days), and median dose of cof fee was 5 cups/d. Systolic and diastolic blood pressure increased by 2.4 (r ange, 1.0 to 3.7) mm Hg and 1.2 (range, 0.4 to 2.1) mm Hg, respectively, wi th coffee treatment compared with control. Multiple linear regression analy sis identified an independent, positive relationship between cups of coffee consumed and subsequent change in systolic blood pressure, independent of age of study participants and study design characteristics. The effect of c offee drinking on systolic and diastolic blood pressure was greater in tria ls with younger participants, Our findings provide support for a relationsh ip between coffee consumption and higher blood pressure. Trials of coffee c essation of longer duration and in persons with hypertension should be perf ormed.