OBJECTIVES : Influenza has resulted in between 140,000 – 810,000 hospitalizations annually since 2010 placing a substantial health burden on people in the United States each year. This study evaluated the risk factors associated with hospitalization among patients with influenza in a real-world setting.

METHODS : Patients with a diagnosis of influenza between 2016-2020 were identified from the Mercy Health electronic health records, which is comprehensive and longitudinal. Hospitalization for influenza was defined as hospitalization on or within 14 days after first influenza diagnosis. Multivariate logistic regression was conducted to determine the risk factors including patient demographics and behaviors, comorbidities, and medications associated with hospitalization.

RESULTS : A total of 65,871 patients (mean age 37 years, 56% female) with influenza were identified. Among demographics and behaviors, older age [age 51-75 and 75+ years vs 22-50 years, Odds ratio (OR), 95% Confidence Interval (95% CI): 1.7, 1.3-2.2 and 2.0, 1.4-3.0, respectively], and current tobacco use (OR, 95% CI: 1.6, 1.3-2.1) significantly increased the risk of hospitalization. Among comorbidities, the significant factors were necrotic conditions of lower respiratory tract (OR, 95% CI: 7.6, 1.4-43.5), paralysis (OR, 95%CI: 5.4, 1.9-15.9), respiratory disorders (OR, 95% CI: 4.7, 3.5-6.3), coagulopathy (OR, 95%CI: 3.0, 1.9-4.6), hypertension (OR, 95% CI: 1.8, 1.3-2.6), anemia (OR, 95% CI: 1.8, 1.2-2.7), neurologic disorders (OR, 95% CI: 1.7, 1.1-2.5), diabetes (OR, 95% CI: 1.6, 1.2-2.1), and renal failure (OR, 95% CI: 1.4, 1.1-1.9). Among medication use, antivirals (OR, 95% CI: 1.8, 1.2-2.7), opioids (OR, 95% CI: 1.6, 1.2-2.0), and antihyperglycemics (OR, 95% CI: 1.5, 1.1-2.1) significantly increased the risk of hospitalization.

CONCLUSIONS : This real-world study identified certain patient demographic (age), behavior (tobacco use), comorbidity (respiratory disorder, paralysis, coagulopathy, hypertension, anemia, neurologic disorders, diabetes, renal failure) and medication use (antiviral, opioid, antihyperglycemic) that were significantly associated with hospitalization among patients with a diagnosis of influenza.