May 11, 2012 (London, United Kingdom) — A new meta-analysis, including the most contemporary studies that have examined coffee consumption and risk of cardiovascular events in a general population, has found that moderate intake may help protect against ischemic stroke .
Presenting the results at the recent European Society of Hypertension (ESH) European Meeting on Hypertension 2012, Dr Lanfranco D’Elia (Federico II University of Naples, Italy) told heartwire : “The first message is that coffee intake is not associated with a higher risk of stroke,” which he says is reassuring. “Second, the analysis showed that low to moderate intake–one to three cups of coffee per day–was associated with lower risk of stroke in the general population, across a wide range of countries, including some in Europe, the US, and Japan.”
However D’Elia stressed that these results apply to the general population only and that findings with regard to coffee intake and risk in those with cardiovascular disease have been conflicting. Nevertheless, he believes that “one coffee a day is not dangerous for people with heart disease.”
Protective effect independent of most identifiable confounders
D’Elia and colleagues performed a meta-analysis of the available prospective studies, including those that estimated baseline coffee consumption and risk of stroke in the general population, from 1966 to 2011. However, the majority of studies included were performed in the late 2000s, including a recent Swedish study and one from the Netherlands.
One to three cups of coffee per day was associated with lower risk of stroke in the general population.
For this analysis, coffee consumption was stratified into moderate (one to three cups/day), high (three to six), and very high (six or more) and compared with the reference category (zero to one). For each study, the values of relative risk (RR) and their confidence interval were extracted and then combined using a random effect model. Eight general-population studies were included in the analysis, for a total of 11 cohorts (484 757 participants, 7272 stroke events, follow-up two to 24 years).
In the pooled analysis, habitual moderate coffee consumption was associated with decreased risk of stroke (RR 0.86, 95% CI 0.75–0.98; p < 0.02).
Stroke risk in the high-consumption category showed a trend in the same direction, toward a reduction (RR 0.87, 95% CI 0.70–1.08; p=0.02), which reached statistical significance upon sensitivity analysis with the exclusion of a single outlier study (RR 0.81, 95% CI 0.70–0.95; p=0.01).
Habitual very high coffee consumption was not associated with any effect on stroke risk (RR 1.05, p=0.71).
D’Elia said that unlike low to moderate coffee intake, both “high” and “very high” consumption showed a significant heterogeneity between studies.
Statistical analysis did not find any significant sources of heterogeneity (length of follow-up, publication year, gender, countries, etc) that affected the relationship between coffee intake and stroke risk, but he noted, “We cannot exclude the potential limitations of the analysis around the standardization of coffee preparation or different types of coffee.
“The results of this meta-analysis, which included prospective studies of samples of the general population, indicate that coffee consumption is not associated with a higher risk of stroke and that actually habitual moderate consumption may exert a protective effect independently from most identifiable confounders,” he concluded.