Nine studies were included: one RCT (n=125); one retrospective nested case-control study (n=240,328); five retrospective cohort studies (n=78,999); a linked case-control study (n=9,829); and a retrospective population-based analysis.
Suitable strategies for reduction of bias were described in the RCT. The authors reported that the observational studies all had adequate descriptions of patient characteristics and only one lacked descriptions of cardiovascular comorbidity. Description of treatment strategy was reported as lacking detail in six of the seven observational studies.
Two cohort studies and a nested case-control study reported a decrease in all-cause mortality in patients treated with statins. One cohort study found no difference.
One cohort study and the linked case-control study showed a decrease in deaths attributable to COPD. Population-based analysis found less COPD mortality in areas with high statin use.
One cohort study reported fewer exacerbations and fewer intubations secondary to COPD in patients who took statins. One observational study showed that decline in lung function parameters were attenuated in statin users. The RCT found no difference in lung function after six months, but improvement in exercise capacity and dyspnoea after exercise was reported.