Epidemiology, Clinical Features, and Prognosis of Elderly Adults with Severe Forms of Influenza A (H1N1)

Objectives To examine epidemiological and clinical data of individuals aged 65 and older with influenza virus A (H1N1) admitted to the intensive care unit (ICU) and to identify independent predictors of ICU mortality. Design Prospective, observational, multicenter study to determine prognostic factors in individuals infected with influenza A (H1N1) admitted to the ICU. Setting One hundred forty-eight Spanish ICUs. Participants Individuals with influenza A (H1N1) confirmed using real-time polymerase chain reaction from April 2009 to July 2011. Measurements Individuals aged 65 and older were compared with younger individuals. A multivariate analysis was conducted to determine independent predictors of mortality in this population. Results One thousand one hundred twenty individuals (129 (11.5%) aged 65) were included. Prevalence of chronic diseases was more common in older individuals. Viral pneumonitis was more frequent in individuals younger than 65 (70.5% vs 54.3%, P<.001). In older individuals, Acute Physiology and Chronic Health Evaluation II score (odds ratio (OR)=1.11, 95% confidence interval (CI)=1.111.20, P=.002), immunosuppression (OR=3.66, 95% CI, 1.3310.03, P=.01) and oseltamivir therapy initiated after 48hours (OR=3.32, 95% CI=1.0210.8, P=.04) were identified as independent variables associated with mortality. Corticosteroid use was associated with a trend toward greater mortality (OR=2.39, 95% CI=0.985.91, P=.06). Conclusion Individuals aged 65 and older with influenza A (H1N1) admitted to the ICU have a higher incidence of underlying diseases than younger individuals and differences in clinical presentation. Early oseltamivir therapy is associated with better outcomes in elderly adults.