Systematic Reviews and Meta-and Pooled Analyses Coffee Consumption and Risk of Stroke: A Dose-Response Meta-Analysis of Prospective Studies Downloaded from

Coffee consumption has been inconsistently associated with risk of stroke. The authors conducted a metaanalysis of prospective studies to quantitatively assess the association between coffee consumption and stroke risk. Pertinent studies were identified by searching PubMed and Embase from January 1966 through May 2011 and by reviewing the reference lists of retrieved articles. Prospective studies in which investigators reported relative risks of stroke for 3 or more categories of coffee consumption were eligible. Results from individual studies were pooled using a random-effects model. Eleven prospective studies, with 10,003 cases of stroke and 479,689 participants, met the inclusion criteria. There was some evidence of a nonlinear association between coffee consumption and risk of stroke (P for nonlinearity ¼ 0.005). Compared with no coffee consumption, the relative risks of stroke were 0.86 (95% confidence interval (95% CI): 0.78, 0.94) for 2 cups of coffee per day, 0.83 (95% CI: 0.74, 0.92) for 3À4 cups/day, 0.87 (95% CI: 0.77, 0.97) for 6 cups/day, and 0.93 (95% CI: 0.79, 1.08) for 8 cups/ day. There was marginal between-study heterogeneity among study-specific trends (I 2 ¼ 12% and I 2 ¼ 20% for the first and second spline transformations, respectively). Findings from this meta-analysis indicate that moderate coffee consumption may be weakly inversely associated with risk of stroke. coffee; meta-analysis; prospective studies; review; stroke Abbreviation: CI, confidence interval. Coffee is one of the most frequently consumed beverages worldwide. Because of the popularity of coffee, even small health effects of coffee could have considerable public health consequences. Compounds in coffee may have either beneficial or unfavorable effects on the cardiovascular system. The phenolic compounds in coffee possess antioxidant capacity and can inhibit the oxidative modification of low density lipoprotein cholesterol (1-3), thereby reducing the atherosclerotic process. On the other hand, regular intake of caffeine has been associated with increased blood pressure (4), and hypertension is a risk factor for cardiovascular disease (5, 6). Coffee consumption may also have effects on serum cholesterol and homocysteine concentrations, oxidation, and inflammation (7). Findings from a recent meta-analysis showed a nonlinear relation between coffee consumption and risk of coronary heart disease (8). While moderate coffee consumption (1-3 cups/day in the United States or 3-4 cups/day in Europe) was associated with a significantly lower risk of coronary heart disease in women and in men and women followed for 10 years, no association was observed for heavy coffee consumption (8). Ample evidence also indicates that coffee consumption is inversely associated with risk of type 2 diabetes (9), which is a risk factor for cardiovascular disease. Whether coffee consumption affects the risk of stroke remains unclear. Results from prospective studies of the association between coffee consumption and stroke risk have not yet been summarized. We conducted a meta-analysis of data from prospective studies to quantitatively assess the relation between coffee consumption and risk of stroke. We performed a dose-response meta-analysis to examine a potential nonlinear association between coffee consumption and stroke