Background Community-acquired pneumonia (CAP) is one of the most common communicable diseases worldwide associated with significant levels of morbidity and mortality causing a substantial economic burden. 30-day hospital readmission rate is often used as a secondary outcome in studies of CAP. This data can be used to define the burden of disease and the reasons for readmissions potentially amenable to intervention.

A systematic review and random meta-analysis were conducted to estimate the pooled 30-day readmission rate of adult patients with CAP and 30-day pneumonia-related/non-pneumonia-related and cardiovascular-related readmission rates of such patients.

Methods MEDLINE, EMBASE, AMED (until October 2017) and reference lists of papers were searched to identify studies of CAP including 30-day hospital readmission rate of adult patients. Each step of the study selection process was conducted by two independent reviewers. The quality was assessed using a pre-tested form based on the Newcastle-Ottawa Scale. Pooled proportions of patients readmitted within 30 days with 95% confidence intervals (CI), were estimated. Additional subgroup analyses were conducted.

Results A total of 63 studies were included in the statistical analysis, covering the period from 1994 to 2017. The pooled 30-day readmission rate estimate was 0.10 (CI 0.08–0.11). High levels of heterogeneity were identified, I²=98.95%. Only two subgroups analysis reported statistically significant differences (p-value <0.05). Retrospective studies had a higher readmission rate of 0.12 (95% CI 0.10 to 0.14, I²=99.39%) compared to prospective studies, 0.07 (95% CI 0.06 to 0.09, I²=93.35%). Europe had significantly lower 30-day readmission rate, 0.08 (95% CI 0.07 to 0.10, I²=94.98%) than North America, which reported 0.11 (95% CI 0.09 to 0.14, I²=99.50%). Non-pneumonia-related readmissions accounted for 0.60 (95% CI 0.48 to 0.72, I²=89.00%) of all 30-day readmissions. Additionally, 0.31 (95% CI 0.25 to 0.37, I²=79.74%) of 30-day readmissions were pneumonia-related, while 0.20 (95% CI 0.14 to 0.26, I²=33.55%) were cardiovascular-related. The studied populations were mostly composed of elderly patients. High levels of heterogeneity may have been due to different selection criteria of included studies and variations among health-care systems and treatment practices.

Conclusion Among all adult patients with CAP, 10% are readmitted to the hospital within 30 days. The majority of all-cause readmissions are non-pneumonia-related, specifically 20% are cardiovascular related. Only one third of 30-day readmissions are due to pneumonia.