Weight and prognosis for influenza A(H1N1)pdm09 infection during the pandemic period between 2009 and 2011: a systematic review of observational studies with meta-analysis

Abstract

Background: In 2009, a novel influenza A(H1N1)pdm09 virus was detected and caused influenza pandemic. It is important to identify the risk factors for severe outcomes. However, inconsistent results regarding the effect of obesity were reported in previous studies.

Methods: We conducted a systematic review to assess the association between obesity and poor prognosis for laboratory-confirmed A(H1N1)pdm09 influenza. We searched three English databases and three Chinese databases for relevant studies from April 2009 to October 2015: PubMed, the Cochrane library, Embase, CNKI, CBM, and Wanfang. Two investigators independently identified eligible articles, assessed quality using NOS, and extracted data. We performed meta-analyses and meta-regressions to estimate the association between weight and poor prognosis for influenza A(H1N1)pdm09 infection, when data were available.

Results: We identified 22 articles enrolling 25,189 laboratory confirmed patients. The pooled estimates indicated obesity significantly increased the risk of fatal and critical complications of influenza A(H1N1)pdm09 infection (for fatal, OR = 1.81, 95% CI: 1.23−2.65; for critical complications, OR = 1.67, 95% CI: 1.13−2.47). However, we found significant interaction between early antiviral treatment and obesity (β = −0.28). After adjustment for early antiviral treatment, relationship between obesity and poor outcomes disappeared (OR = 1.14, 95% CI: 0.94−1.39).

Conclusions: The results of the meta-analyses showed obesity significantly increased the risk of death, critical complications, and severe complications for influenza A(H1N1)pdm09 infection, especially among high-quality studies and in Asia region. Importantly, the result from our meta-regression indicated that the conclusion should be interpreted with caution, because early antiviral treatment might be a key confounding factor.

Keywords:

• Influenza A(H1N1)pdm09
• meta-analysis
• obesity
• systematic review

Disclosure statement

The authors declare that there are no conflicts of interest.

The funders had no role in study design, data collection, and analysis, decision to publish, or preparation of the manuscript. The corresponding author had full access to all study data and had final responsibility for the decision to submit for publication.

Funding information

The study is supported by The Capital Health Research and Development of Special (2014-1-1011), Beijing Municipal Science and Technology Commission (D141100003114002), Beijing Talents Fund (2014000021223ZK36), and Beijing Health System High Level Health Technology Talent Cultivation Plan (2013-3-098).