Is COPD associated with increased mortality and morbidity in hospitalized pneumonia? A systematic review and meta-analysis.

This review aimed to investigate whether chronic obstructive pulmonary disease (COPD) is associated with increased mortality and morbidity in patients hospitalized with community-acquired pneumonia (CAP). EMBASE, PubMed and Web of Science were searched for cohort studies and case-control studies investigating the impact of COPD on CAP. The primary outcome was all-cause mortality, and secondary outcomes included length of hospital stay, intensive care unit (ICU) admission and need for mechanical ventilation. Methodological quality was assessed using the Newcastle-Ottawa Scale. The Mantel-Haenszel method and inverse variance method were used to calculate pooled relative risks (RRs) and mean differences (MD), respectively. Eleven studies (nine cohort studies and two case-control studies), involving 257 958 patients, were included. The overall methodological quality was high. COPD was not associated with increased mortality in hospitalized CAP patients (RR, 1.20; 95% confidence interval (CI): 0.92-1.56; P = 0.19; I(2)  = 55%) in cohort studies, and was associated with reduced mortality in case-control studies (RR, 0.82; 95% CI: 0.74-0.90; P < 0.0001; I(2)  = 80%). COPD was not associated with longer hospital stay (MD, 0.11; 95% CI: -0.42 to 0.64; P = 0.68; I(2)  = 21%), more frequent ICU admission (RR, 0.97; 95% CI: 0.70-1.35; P = 0.87; I(2)  = 65%), and more need for mechanical ventilation (RR 0.91, 95% CI: 0.71-1.16; P = 0.44; I(2)  = 4%).The current available evidence indicates that COPD may not be associated with increased mortality and morbidity in patients hospitalized with CAP. This conclusion should be re-evaluated by prospective population-based cohort studies.