Morbid Obesity as a Risk Factor for Hospitalization and Death Due to 2009 Pandemic Influenza A(H1N1) Disease

Abstract

BackgroundSevere illness due to 2009 pandemic A(H1N1) infection has been reported among persons who are obese or morbidly obese. We assessed whether obesity is a risk factor for hospitalization and death due to 2009 pandemic influenza A(H1N1), independent of chronic medical conditions considered by the Advisory Committee on Immunization Practices (ACIP) to increase the risk of influenza-related complications.Methodology/Principal FindingsWe used a case-cohort design to compare cases of hospitalizations and deaths from 2009 pandemic A(H1N1) influenza occurring between April–July, 2009, with a cohort of the U.S. population estimated from the 2003–2006 National Health and Nutrition Examination Survey (NHANES); pregnant women and children <2 years old were excluded. For hospitalizations, we defined categories of relative weight by body mass index (BMI, kg/m2); for deaths, obesity or morbid obesity was recorded on medical charts, and death certificates. Odds ratio (OR) of being in each BMI category was determined; normal weight was the reference category. Overall, 361 hospitalizations and 233 deaths included information to determine BMI category and presence of ACIP-recognized medical conditions. Among ≥20 year olds, hospitalization was associated with being morbidly obese (BMI≥40) for individuals with ACIP-recognized chronic conditions (OR = 4.9, 95% CI 2.4–9.9) and without ACIP-recognized chronic conditions (OR = 4.7, 95%CI 1.3–17.2). Among 2–19 year olds, hospitalization was associated with being underweight (BMI≤5th percentile) among those with (OR = 12.5, 95%CI 3.4–45.5) and without (OR = 5.5, 95%CI 1.3–22.5) ACIP-recognized chronic conditions. Death was not associated with BMI category among individuals 2–19 years old. Among individuals aged ≥20 years without ACIP-recognized chronic medical conditions death was associated with obesity (OR = 3.1, 95%CI: 1.5–6.6) and morbid obesity (OR = 7.6, 95%CI 2.1–27.9).Conclusions/SignificanceOur findings support observations that morbid obesity may be associated with hospitalization and possibly death due to 2009 pandemic H1N1 infection. These complications could be prevented by early antiviral therapy and vaccination.

Working-age adults with diabetes experience greater susceptibility to seasonal influenza: a population-based cohort study

“…Second, as the present study was observational, other unrecognised confounders may affect our findings. For example, obesity has emerged as a risk factor for hospitalisation and severe outcomes in pH1N1 cases [34][35][36]. It remains unclear from the pH1N1 literature whether obesity is an independent risk factor for influenza or whether the association between obesity and severe outcomes of influenza is itself confounded by diabetes, cardiovascular disease and other obesity-related comorbidities [36].…”

“…It remains unclear from the pH1N1 literature whether obesity is an independent risk factor for influenza or whether the association between obesity and severe outcomes of influenza is itself confounded by diabetes, cardiovascular disease and other obesity-related comorbidities [36]. One recent study of the NHANES cohort found a consistent association between obesity and pH1N1 hospitalisations/death, after stratifying by comorbidity, suggesting a true diathesis [34]. In the seasonal influenza literature, Kwong et al have demonstrated an association between obesity and increased respiratory hospitalisations, after adjusting for diabetes and cardiovascular disease [37].…”

Impact of obesity on mortality in hospitalized patients with pneumonia due to 2009 H1N1 Influenza A virus versus other etiologies.

“…[4][5][6][7] Animal studies indicate that the production of interferon is significantly decreased in diet-induced, obese mice when compared to lean, control animals. 15,16 Decreased production of interferon in obese patients may explain the poor outcomes associated with pneumonia due to 2009 H1N1 influenza A virus.…”

“…Recent reports of acutely ill hospital- poor outcomes. [4][5][6] Obese patients with pneumonia due to 2009 H1N1 were more likely to require ICU care due to severe pneumonia with respiratory failure and acute respiratory distress syndrome (ARDS). 7 On the other hand, a meta-analysis published in 2009 indicated that hospitalized, acutely ill, obese patients were protected from poor outcomes.…”

Driving pressure in obese ventilated patients: another brick in the (chest) wall

“…Obesity is associated with significant complications, and an increase in the mortality of obese patients after hospital admission compared to non-obese patients is justified [1]. The proportion of obesity in patients presenting with acute respiratory distress syndrome (ARDS) has not been investigated systematically, but data from the influenza A (H1N1) pandemic in 2009 suggested that obese patients were overrepresented compared to the general population [2]. The management of ARDS in patients with obesity is a special challenge, since obesity and severe obesity are associated with marked derangements in lung and chest wall mechanics [3].…”