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Open Access Highly Accessed Research article

Obesity survival paradox in pneumonia: a meta-analysis

Wei Nie1, Yi Zhang2, Sun Ha Jee3, Keum Ji Jung3, Bing Li1* and Qingyu Xiu1*

Author Affiliations

1 Department of Respiratory Medicine, Shanghai Changzheng Hospital, Second Military Medical University, 415 Fengyang Road, Shanghai 200003, China

2 Department of Clinical Nutrition, The 452nd Hospital of PLA, Chengdu 610000, Sichuan, China

3 Department of Epidemiology and Health Promotion, Graduate School of Public Health, Yonsei University, Seoul 120-749, Korea

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BMC Medicine 2014, 12:61  doi:10.1186/1741-7015-12-61

Published: 10 April 2014

Abstract

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, I2 = 87%). In the dose–response analysis, the estimated summary RR of pneumonia per 5 kg/m2 increase in BMI was 1.04 (95% CI 1.01 to 1.07, P = 0.01, I2 = 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, I2 = 34%). The estimated summary RR of mortality per 5 kg/m2 increase in BMI was 0.95 (95% CI 0.93 to 0.98, P < 0.01, I2 = 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.

Keywords:
Body mass index; Obesity; Pneumonia; Dose–response relationship; Meta-analysis