Both underweight and morbidly obese adults with influenza were more likely to be hospitalized compared with normal body weight adults, according to study results published in Influenza and Other Respiratory Viruses.

Nasopharyngeal swabs from both outpatient and hospitalized adults with symptoms of influenza-like illness were tested for influenza and other common respiratory pathogens. Outpatient and hospitalization groups were compared to evaluate risk factors for hospitalization. In pediatric participants, there were no significant interactions between body mass index and the pathogen groups.

Of the 4778 participants who enrolled in the study; 2636 had severe influenza-like illness. A total of 778 individuals 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 morbidly obese compared with normal-weight adults (odds ratio in obese adults, 8.96 vs 1.35; odds ratio in morbidly obese adults, 35.13 vs 5.58, respectively). Furthermore, obese adults with H1N1 had a 6-fold increase in odds of hospitalization compared with H3N2 and B.

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The investigators wrote, “We have demonstrated that adults that are underweight or morbidly obese are more likely to be hospitalized from an influenza-like illness, regardless of the causative agent of the illness, than normal-weight adults.”

They added “Clinicians should keep a patient’s body mass index in mind when evaluating risk and deciding on a course of treatment.”


Moser J-AS, Galindo-Fraga A, Ortiz-Hernández AA, et al. Underweight, overweight, and obesity as independent risk factors for hospitalization in adults and children from influenza and other respiratory viruses [published online December 4, 2018]. Influenza Other Respir Viruses. doi:10.1111/irv.12618