The impact of obesity and timely antiviral administration on severe influenza outcomes among hospitalized adults.

Obesity was identified as a risk factor for severe influenza during the 2009 influenza A(H1N1)pandemic, but evidence of this association has been mixed since. Post-pandemic antiviral treatment guidelines may have increased antiviral treatment among obese individuals. A prospective study of adults hospitalized with laboratory-confirmed influenza in Detroit, Michigan in 2011-2012 and 2012-2013 was conducted. Patient information was collected from interviews and medical chart abstraction. Obese (BMI ≥ 30) and non-obese (BMI < 30) participants were compared. Late antiviral treatment (>2 days from symptom onset), obesity (30 ≤ BMI < 40), and morbid obesity (BMI ≥ 40) were evaluated as predictors of lower respiratory tract disease (LRD), ICU admission, and length of stay (LOS) using logistic regression and inverse probability weighted models. Forty-eight participants were included in the study after exclusions and all patients received antiviral treatment. Participants who were obese were significantly more likely to have a cough and to take steroids than non-obese participants, and had a shorter time from hospital admission to antiviral treatment (median time from admission to treatment of 0 days for obese patients and 1 day for non-obese patients [P = 0.001]). In all models, late antiviral treatment was associated with increased odds of LRD (OR: 3.9 [1.1,15.9] in fully adjusted model). After adjustment for treatment timing, the odds of ICU admission (OR: 6.4 [0.8,58.2] to 7.9 [0.9, 87.1]) and LRD (OR: 3.3 [0.5, 23.5] to 4.0 [0.6, 35.0]) associated with morbid obesity increased. Obese individuals were treated with antivirals earlier than others. Late antiviral treatment was associated with severe influenza in the hospital.