Body mass index and risk of pneumonia: a systematic review and meta‐analysis

Summary The aims of our meta‐analysis were to examine the pattern and gender's influence on body mass index ( BMI ) – pneumonia relationship. Published studies were searched from PubMed , W eb of S cience, C ochrane L ibrary databases using keywords of pneumonia, BMI and epidemiologic studies. Random‐effects analysis was applied to estimate pooled effect sizes from individual studies. The C ochrane Q ‐test and index of heterogeneity ( I 2 ) were used to evaluate heterogeneity, and E gger's test was used to evaluate publication bias. Random‐effects meta‐regression was applied to examine the pattern and gender's influence on BMI –pneumonia relationship. A total of 1,531 studies were initially identified, and 25 studies finally were included. The pooled relative risk ( RR ) and meta‐regression model revealed a J ‐shaped relationship between BMI and risk of community‐acquired pneumonia (underweight, RR 1.8, 95% confidence interval [ CI ], 1.4–2.2, P < 0.01; overweight, 0.89, 95% CI , 0.8–1.03, P , 0.1; obesity, 1.03, 95% CI , 0.8–1.3, p. 8) and U ‐shaped relationship between BMI and risk of influenza‐related pneumonia (underweight, RR 1.9, 95% CI , 1.2–3, P < 0.01; overweight, 0.89, 95% CI , 0.79–0.99, P , 0.03; obesity, 1.3, 95% CI , 1.05–1.63, p. 2; morbidity obesity, 4.6, 95% CI , 2.2–9.8, P < 0.01); whereas, no difference in risk of nosocomial pneumonia was found across the BMI groups. Gender difference did not make significant contribution in modifying BMI –pneumonia risk relationship.