To examine trends in mortality, morbidity, hospital length and cost of stay in influenza patients with low and high comorbidity index.

METHODS: The latest available 2016 National Inpatient Sample (NIS) data set from the Healthcare Cost and Utilization Project was utilized in order to determine the number of hospital admissions for patients with influenza. Propensity score matched analysis was conducted to compare mortality hospital, LOS and costs in patients with low and high comorbidity index. Thirty comorbidities were assessed using Elixhauser scoring. Multivariate logistic regression was conducted to assess predictor variables for LOS and costs.

RESULTS:

In 2016, there were an estimated 145,360 hospitalizations with a diagnosis of influenza. Approximately 54% and 46% had comorbidity index of <3 and ≥ 3, respectively. The mean age was 43.1 (SD 28.3) and 66.2 (SD 15.8) in low and high comorbidity groups, respectively. 51.8% and 52.6% were female in low and high comorbidity groups, respectively. Most common comorbidities (more than 10%) were congestive heart failure (19.8%), cardiac arrhythmias (23.5%), hypertension (37.4%), chronic pulmonary disease (40.5%), diabetes (15.7% uncomplicated, 12.1% complicated), renal failure (16.7%) and depression (16.1%). The propensity score matched hospital LOS was 4.4 and 7.3 days, with a statistically significant difference of 2.9 days (SE 0.44, P<0.05), in low and high comorbidity groups, respectively. The propensity score matched hospital charges were $29,038 and $83,301, with a statistically significant difference of $54,263 (SE $6178, P<0.05), in low and high comorbidity groups, respectively. Mortality rate was 1.2% and 5.9% in low and high comorbidity groups, respectively (P<0.0001).

CONCLUSIONS: Influenza patients with high comorbidity index incur significantly longer hospital length of stay and nearly 3 times the costs and mortality compared to patients with low comorbidity index. There is a need for better treatment management for influenza patients with high comorbidity index.