Summary effects of statins on PAP (A,B) and 6-minute walk distance (C,D) in COPD (A,C) and PAH (B,D). PAP, pulmonary arterial pressure; WMD, weighted mean difference; CI, confidence interval; 6MWD, 6-minute walking distance; PAH, pulmonary arterial hypertension; COPD, chronic obstructive pulmonary disease.