# Effect of Oseltamivir Use on Follow-Up Stroke Mortality

## TL;DR

This study finds that using Oseltamivir during influenza does not increase stroke risk but may reduce mortality in those with a history of stroke.

## Contribution

The study reveals a potential survival benefit of Oseltamivir in stroke patients with influenza, previously unexplored.

## Key findings

- Oseltamivir use was not linked to increased stroke risk in individuals without prior stroke.
- Oseltamivir users with a history of stroke had lower mortality rates.
- The mortality benefit remained significant after adjusting for age, sex, and comorbidities.

## Abstract

Background/Objectives: Evidence has indicated an increased risk of stroke in individuals with influenza infection, and the administration of Oseltamivir revealed a lower stroke risk in these individuals. However, the impacts of Oseltamivir and stroke remain limited. Methods: The data used in this retrospective cohort study were extracted from the Taiwan National Health Insurance Research Database (NHIRD), which included 281,420 Oseltamivir users and 13,394,652 patients between 1 January 2009 and 31 December 2018. The Oseltamivir group was younger (age 40.1 ± 15.3 years) and had a lower prevalence of comorbidities compared to the non-user group (age 46.2 ± 16.0 years). Stroke incidence and mortality were compared using multivariable Cox proportional hazards models. Results: We compared the incidence of ischemic stroke among individuals without a history of ischemic stroke, stratified by Oseltamivir use. After adjusting for age, sex, and comorbidities, Oseltamivir use was not associated with a significantly different risk of stroke (adjusted HR = 1.02, 95% CI: 0.96–1.08; p = 0.511). The mortality among individuals with a history of ischemic stroke, being Oseltamivir users (n = 2502), exhibited a lower cumulative mortality rate compared to non-users (4.08% vs. 6.45%). The association remained significant after multivariable adjustment, with an adjusted hazard ratio for mortality of 0.74 (95% CI: 0.61–0.89; p = 0.002). Conclusions: In this large population-based cohort of patients without a history of ischemic stroke, Oseltamivir use during influenza infection was not associated with stroke incidence after adjusting for age, sex, and comorbidities. Notably, Oseltamivir use in patients with a history of ischemic stroke was associated with reduced all-cause mortality, suggesting a potential survival benefit that warrants further investigation.