Habitual coffee consumption and risk of hypertension: a systematic review and meta-analysis of prospective observational studies.

BACKGROUND In 2 meta-analyses of randomized controlled trials, increased coffee intake was associated with slightly higher blood pressure. However, these trials were short in duration (<85 d). OBJECTIVE We conducted a systematic review and meta-analyses of long-term prospective studies that examined the association of habitual coffee consumption with risk of hypertension. DESIGN We searched electronic databases (MEDLINE, EMBASE, Agricola, and Cochrane Library) through August 2009 with the use of a standardized protocol. Eligible studies were prospective cohort trials that examined the association of coffee consumption with incident hypertension or blood pressure. RESULTS From 6 prospective cohort studies, a total of 172,567 participants and 37,135 incident hypertension cases were included. Mean follow-up ranged from 6.4 to 33.0 y. Compared with the lowest consumption [<1 cup (≈237 mL)/d], the pooled relative risks (RRs) for hypertension were 1.09 (95% CI: 1.01, 1.18) for the next higher category (1-3 cups/d), 1.07 (95% CI: 0.96, 1.20) for the second highest category (3-5 cups/d), and 1.08 (95% CI: 0.96, 1.21) for the highest category (>5 cups/d). A dose-response meta-analysis showed an inverse "J-shaped" curve (P for quadratic term < 0.001) with hypertension risk increasing up to 3 cups/d (RR for comparison of 3 with 0 cups/d: 1.07; 95% CI: 0.97, 1.20) and decreasing with higher intakes (RR for comparison of 6 with 0 cups/d: 0.99; 95% CI: 0.89, 1.10). CONCLUSION The results suggest that habitual coffee consumption of >3 cups/d was not associated with an increased risk of hypertension compared with <1 cup/d; however, a slightly elevated risk appeared to be associated with light-to-moderate consumption of 1 to 3 cups/d.