#13,724
Early on in the 2009 H1N1 pandemic (see H1N1 Morbidity And Previously Existing Conditions) we saw reports of unusual numbers of obese influenza patients - a previously unrecognized risk group - populating intensive care facilities around the world.
Obesity - and particularly morbid obesity - was increasingly mentioned as a possible risk factor, along with asthma, diabetes, and immune disorders.That notion took a hit a few months later, when - during an ACIP meeting held at the end of July, 2009 - evidence was presented that showed that the incidence of hospitalizations among those listed as obese by their BMI was practically the same as their prevalence in society.
Roughly 34% of Americans are obese, and roughly 38% of those hospitalized met that criteria. While 6% are morbidly obese (BMI > 40), they only made up 7% of the hospitalized cases.Two months later, in Study: Half Of ICU H1N1 Patients Without Underlying Conditions, it became apparent that while pre-existing risk factors were important, they were not the sole reason behind flu victims ending up in intensive care.
A few months later, Eurosurveillance Journal published a Study: H1N1 Hospitalization Profiles, reported similar results:
- The most common risk factor in admission to intensive care was chronic respiratory disease followed by chronic neurological disease, asthma and severe obesity.
- 51% of hospitalized cases and 42% of ICU cases were not in a recognized risk group.
In 2011 (see Extreme Obesity: A Novel Risk Factor For A Novel Flu), the IDSA’s journal Clinical Infectious Diseases published a study called A Novel Risk Factor for a Novel Virus: Obesity and 2009 Pandemic Influenza A (H1N1), that found:
Extreme obesity associated with higher risk of death for 2009 H1N1 patients
[EMBARGOED FOR JAN. 5, 2011] For those infected with the 2009 pandemic influenza A (H1N1) virus, extreme obesity was a powerful risk factor for death, according to an analysis of a public health surveillance database.
In a study to be published in the February 1, 2011, issue of Clinical Infectious Diseases, researchers associated extreme obesity with a nearly three-fold increased odds of death from 2009 H1N1 influenza. Half of Californians greater than 20 years of age hospitalized with 2009 H1N1 were obese.Despite a lack of consensus, for the past few years the CDC has cited `people with extreme obesity (i.e., body-mass index is equal to or greater than 40)' on their list of High Risk groups for severe influenza.
The controversy continues, however.Last February, in Study: Obesity & Influenza-Like-Illness (ILI) Severity, we saw a 2018 paper appearing in the International Journal of Obesity, that found quite the opposite; a four year (2010-2014) study of ER visits for influenza-like-illness (ILI), found that obesity was not linked to a greater risk of hospitalization.
Epidemiology and population health
Is weight associated with severity of acute respiratory illness?
Elizabeth E. Halvorson,Timothy R. Peters, Joseph A. Skelton, Cynthia Suerken, Beverly M. Snively & Katherine A. Poehling Conclusion
Overweight and obesity were not associated with increased risk of hospitalization during winter respiratory seasons in children or adults.
Alas, science isn’t always consistent, neat, or tidy. Results can vary widely depending upon the design, size, location, and timing of a study (see When Studies Collide (Revisited)), and conflicting findings are more common than one might suspect.
This is the primary reason why I try to present as much relevant context as possible in these blogs, since it is far too easy to cherry pick studies to back up a particular point.Entering the fray this week - this time published in Influenza & Other Respiratory Viruses - is a study that finds both low and high BMI as risk factors for hospitalization with flu or other respiratory infection.
The entire open access study is available online at the link below. I've only included some pertinent excerpts.
Underweight, overweight, and obesity as independent risk factors for hospitalization in adults and children from influenza and other respiratory viruses
Joe‐Ann S. Moser, Arturo Galindo‐Fraga, Ana A. Ortiz‐Hernández, Wenjuan Gu, Sally Hunsberger, Juan‐Francisco Galán‐Herrera, María Lourdes Guerrero,… See all authors
First published: 04 December 2018
https://doi.org/10.1111/irv.12618
Background
The relationship between obesity and risk of complications described during the 2009 influenza pandemic is poorly defined for seasonal influenza and other viral causes of influenza‐like illness (ILI).
Methods
An observational cohort of hospitalized and outpatient participants with ILI was conducted in six hospitals in Mexico. Nasopharyngeal swabs were tested for influenza and other common respiratory pathogens.
Results
A total of 4778 participants were enrolled in this study and had complete data. A total of 2053 (43.0%) had severe ILI. Seven hundred and seventy‐eight (16.3%) were positive for influenza, 2636 (55.2%) were positive for other viral respiratory pathogens, and 1364 (28.5%) had no respiratory virus isolated. Adults with influenza were more likely to be hospitalized if they were underweight (OR: 5.20), obese (OR: 3.18), or morbidly obese (OR: 18.40) compared to normal‐weight adults.
Obese adults with H1N1 had a sixfold increase in odds of hospitalization over H3N2 and B (obese OR: 8.96 vs 1.35, morbidly obese OR: 35.13 vs 5.58, respectively) compared to normal‐weight adults.
In adults with coronavirus, metapneumovirus, parainfluenza, and rhinovirus, participants that were underweight (OR: 4.07) and morbidly obese (OR: 2.78) were more likely to be hospitalized as compared to normal‐weight adults. All‐cause influenza‐like illness had a similar but less pronounced association between underweight or morbidly obesity and hospitalization.
Conclusions
There is an increased risk of being hospitalized in adult participants that are underweight or morbidly obese, regardless of their viral pathogen status. Having influenza, however, significantly increases the odds of hospitalization in those who are underweight or morbidly obese.
As always, it is important to look at the study's design, and its limitations. The authors caution:
One significant limitation to our study is that it enrolled participants that sought medical care for an influenza‐like illness. It is not a population‐based study that can accurately assess the risk that body mass confers for infection. Additionally, the study cannot differentiate within the NIRV group between those with true infections (but not detected on the multiplex platform), or those with non‐infectious etiologies of the respiratory symptoms.(Continue . . . )
In conclusion, our findings suggest that adults, who are underweight or morbidly obese, even if they do not have chronic conditions that increase the risk of influenza‐related complications, may be at increased risk of developing severe disease due to seasonal influenza infection as well as other respiratory viral infections. Clinicians should keep a patient's body mass index in mind when evaluating risk and deciding on a course of treatment.
Despite being personally `gravitationally challenged', I'd never argue that maintaining a `normal BMI' doesn't provide appreciable health benefits.
It also seems likely that those benefits would extend to a lower risk of hospitalization and/or death from influenza and other respiratory infections.So, despite a string of conflicting studies, I'm assuming my extra weight - along with my age - increase my risk factors, and I'll act accordingly; I get the flu shot every year, use hand sanitizer like I own stock in the company, and will take aggressive steps (i.e. antivirals) should my first two lines of defense fail me.
