Obesity survival paradox in pneumonia: a meta-analysis

BACKGROUND: It is unclear whether an 'obesity survival paradox' exists for pneumonia. Therefore, we conducted a meta-analysis to assess the associations between increased body mass index (BMI), pneumonia risk, and mortality risk. METHODS: Cohort studies were identified from the PubMed and Embase databases. Summary relative risks (RRs) with their corresponding 95% confidence intervals (CIs) were calculated using a random effects model. RESULTS: Thirteen cohort studies on pneumonia risk (n = 1,536,623), and ten cohort studies on mortality (n = 1,375,482) were included. Overweight and obese individuals were significantly associated with an increased risk of pneumonia (RR = 1.33, 95% CI 1.04 to 1.71, P = 0.02, I(2) = 87%). In the dose-response analysis, the estimated summary RR of pneumonia per 5 kg/m(2) increase in BMI was 1.04 (95% CI 1.01 to 1.07, P = 0.01, I(2) = 84%). Inversely, overweight and obese subjects were significantly associated with reduced risk of pneumonia mortality (RR = 0.83, 95% CI 0.77 to 0.91, P < 0.01, I(2) = 34%). The estimated summary RR of mortality per 5 kg/m(2) increase in BMI was 0.95 (95% CI 0.93 to 0.98, P < 0.01, I(2) = 77%). CONCLUSIONS: This meta-analysis suggests that an 'obesity survival paradox' exists for pneumonia. Because this meta-analysis is based on observational studies, more studies are required to confirm the results.