Comparison of influenza hospitalization outcomes among adults, older adults, and octogenarians: A US national population-based study

Abstract Objectives This study sought to more fully elucidate the age-related trends in influenza mortality with a secondary goal of uncovering implications for treatment and prevention. Methods In this retrospective cohort analysis of data from the Nationwide Readmission Database, patients with influenza as a primary or secondary discharge diagnosis were separated into three age groups: 55,638 adults aged 20-64, 36,862 older adults aged 65-79, and 41,806 octogenarians aged ≧80. Propensity score (PS) weighting was performed to isolate age from other baseline differences. Crude and PS-weighted hazard ratios (HR) were calculated from the in-hospital all-cause 30-day mortality rate. Admission threshold bias was minimized by comparison of influenza with bacterial pneumonia mortality. Results Adults aged 20-64 experienced higher in-hospital 30-day mortality compared to older adults aged 65-79 (HR: 0.66; 95%CI: 0.55-0.79). Octogenarians had the highest mortality rate, but this was statistically insignificant compared to the adult cohort (HR: 1.09; 95%CI: 0.94-1.27). This trend was not explained by admission threshold bias: the 30-day mortality rate due to in-hospital bacterial pneumonia increased consistently with age (older adult HR: 1.45; 95%CI: 1.32-1.59; octogenarian HR: 1.99; 95%CI: 1.82-2.18). Conclusions Adults aged 20-64 and octogenarians were more likely to suffer from all-cause 30-day mortality during influenza hospitalization compared to older adults aged 65-79. These data emphasize the importance of prevention and suggest the need for more tailored treatment interventions based on risk stratification that includes age.