Randomised, double-blind, single-blind, placebo-controlled trials (RCTs), observational cohort (retrospective and prospective), case-controlled studies and population-based analyses of statin therapy in patients with chronic obstructive pulmonary disease (COPD) were eligible for inclusion in the review. Experimental and laboratory based studies were excluded.
Eligible outcomes were: exacerbation episodes or time to exacerbation; intubations; mortality (all cause, COPD or COPD hospital); respiratory related emergency department visits; Decline in FEV1 (forced expiratory volume) or FVC (forced vital capacity); increase in exercise time on treadmill; C-reactive protein levels or changes; COPD hospitalisation.
COPD was diagnosed according to hospital definitions, Health Maintenance Organisation registry coding, International Classification of Diseases, more than two pulmonary function tests six months apart, FEV1/ FVC ratios, prescription patterns and self reporting. Disease severity varied across studies (37.3 to 77.4 FEV1 or measured by Global Initiative on Obstructive Lung Disease) or was not reported. Statins used were atorvastatin, simvastatin, pravastatin, not recorded or recorded as other statin. Statins were used alone or in combination. Exposure to statins was between three months and more than one year or not recorded. Comparators for use of statins were no use or placebo.
Two reviewers independently assessed studies for inclusion. Disagreements were resolved by consensus with a third reviewer.