SAN DIEGO, CA—A higher influenza severity was seen in obese patients hospitalized during the 2011–2012 and 2012–2013 influenza season, results from a prospective study presented at IDWeek 2015 showed.

“Notably, we found that late treatment with oseltamivir, outside of the CDC-recommended 48 hour window, was associated with increased rates of pneumonia and ICU admission,” reported lead study author Emily T. Martin, MPH, PhD. “It is critical to consider confounding by timing of antivirals when evaluating risk factors for severe influenza infection.”

During the 2009 influenza A/H1N1 pandemic, individuals who were obese had increased disease severity and mortality. Researchers from the University of Michigan School of Public Health, Ann Arbor, MI, and colleagues set out to determine influenza outcomes and risk factors for lower-pulmonary disease (LPD) and other severe complications, among obese patients. The team prospectively identified hospitalized patients with laboratory-confirmed influenza (n=55) during the 2011–2012 and 2012–2013 flu seasons. Almost half (47%) had Class I–III Obesity, defined as a body mass index (BMI) ≥30.

Treatment with oseltamivir was started in patients with obesity faster upon symptom onset (median 2 days vs. 3 days; mean 3.3 vs. 5.2 days; P=0.04). After adjusting for administration of antivirals within 2 days of symptoms onset, researchers found obesity was associated with intensive care unit admission (odds ratio [OR] 6.02, 95% CI: 1.1, 34.5; P=0.04). Lower pulmonary disease was numerically higher as well, but did not reach statistical significance (OR 3.4, 95% CI: 0.9, 12.7).

Obese patients had shorter duration of stay after controlling for the timely administration of antivirals (2.1 less days, 95% CI: 0.2–3.6; P=0.03), Dr. Martin noted.

“Late antiviral administration was related to ICU admissions (OR 7.5, 95% CI: 1.02, 54.5; P=0.047) and lower-pulmonary disease (OR 5.8, 95% CI: 1.4, 24.3; P=0.02) after adjusting for factors such as poorer health status, obesity, steroid use, and diabetes,” she reported.