Fractures and fall injuries after hospitalization for seasonal influenza—a national retrospective cohort study

SUMMARY: In this retrospective cohort study of 6604 adults, 65 years or older, admitted with seasonal influenza at Swedish hospitals, and 330,200 age- and sex-matched controls from the general population admitted for other reasons, were included. Patients with influenza had increased risk of fall injuries and fractures compared to controls. INTRODUCTION: Fractures and fall injuries often lead to disability, increased morbidity, and mortality. Older adults are at higher risk of influenza-related complications such as pneumonia, cardiovascular events, and deaths, but the risk of fractures and fall injuries is unclear. The primary objective of this study was to investigate the risk of fractures and fall injuries in older patients after admission with seasonal influenza. METHODS: In this retrospective cohort study of 6604 adults, 65 years or older, admitted with seasonal influenza at Swedish hospitals (from December 1, 2015, to December 31, 2017) and 330,200 age- and sex-matched controls from the general population and admitted for other reasons, the risk of fracture or fall injury was investigated. RESULTS: The mean (SD) age of the 6604 influenza patients was 80.9 (8.1) years and 50.1% were women. During the first year after hospital discharge, there were 680 (10.3%) patients suffering from a fracture or fall injury among the patients with influenza, and 25,807 (7.8%) among the controls, corresponding to incident rates of 141 (95% CI, 131–152) and 111 (95% CI, 110–112) fractures or fall injuries per 1000 person-years respectively, translating to a significantly increased risk of fracture or fall injury in a Cox regression model (hazard ratio (HR) 1.28 (95% CI, 1.19–1.38)), a risk that was maintained after multivariable adjustment (HR 1.22 (95% CI 1.13–1.31)). CONCLUSIONS: Older adults admitted with influenza diagnosis have an increased risk of fracture or fall injury during the first year after discharge. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00198-021-06068-1.