Incidence of Influenza-associated Neurologic and Psychiatric Complications Requiring Hospitalization in Children Ages 5-17 Years.

Background: The spectrum and incidence of influenza-associated neuropsychiatric complications are not well-characterized. The objective of this study was to define the incidence of specific neurologic and psychiatric complications associated with influenza in children and adolescents.

Methods: We assembled a retrospective cohort of children 5-17 years of age with an outpatient or emergency department International Classification of Diseases, 10th revision influenza diagnosis and enrolled in Tennessee Medicaid from 2016 to 2020. Serious neurologic or psychiatric complications requiring hospitalization were identified using a validated algorithm. Incidence rates of complications were expressed per 100,000 person-weeks of influenza and 95% confidence intervals (CIs) were reported.

Results: A total of 156,661 influenza encounters (median age of 9.3 years) were included. The overall incidence of neurologic complications was 30.5 (95% CI: 24.0-38.6) per 100,000 person-weeks of influenza and 1880.9 (95% CI: 971.9-3285.5) among children with an underlying neurologic comorbidity. The distribution of antiviral treatment was similar among those with and without neurologic or psychiatric complications. The overall incidence of psychiatric complications was 20.2 (95% CI: 15.1-27.0) per 100,000 person-weeks of influenza and 111.8 (95% CI: 77.9-155.5) among children with an underlying psychiatric comorbidity. Seizures (17.5, 95% CI: 12.8-23.9) were the most common neurologic complications whereas encephalitis (0.5, 95% CI: 0.02-2.5) was rare. Mood disorders (17.5, 95% CI: 12.8-23.9) were the most frequent psychiatric complications and self-harm events (0.9, 95% CI: 0.3-3.3) were the least common.

Discussion: Our findings reveal that the incidence of neuropsychiatric complications of influenza is overall low; however, the incidence among children with underlying neurologic or psychiatric condition is significantly higher than among children without these conditions.