PDE5A and Headache: Fig. 4a shows a total 531 of 891 patients suffering AE in the PDE5-Is arm compared to 191 of 450 in controls, a risk ratio of 2.11 (95% CI 1.66 to 2.67). Among the AEs, headache (Fig. 4b) was the most frequent event reported, with a total of 191 of 1205 patients in the PDE5-Is arm compared to 27 of 615 in controls with a risk ratio of 2.99 (95% CI 2.22 to 4.04). Other common AEs were flushing, dyspepsia and upper respiratory tract complains (Fig. 4c,d,e), with an odds ratio of 4.71 (95% CI 3.19 to 6.95), 3.15 (95%CI 1.86 to 5.35) and 2.66 (95% CI 1.85 to 3.84), respectively.