Fractures and Fall Injuries after Hospitalization for Seasonal Influenza - A National Retrospective Cohort Study

Abstract

Background: 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 older adults (≥65 years) admitted with seasonal influenza at Swedish hospitals (from December 1st 2015 to December 31st 2017) and 330200 age and sex matched controls from the general population and admitted for other reasons, the risk of fracture or fall injury was investigated. Findings: 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%) fractures or fall injuries among the patients with influenza and 25807 (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 1·28 (95% CI, 1·19-1·38)). Interpretation: Older adults admitted with influenza diagnosis, have increased risk of fracture or fall injury during the first year after discharge, further supporting the need to prevent influenza by vaccination. Funding: The Swedish Research Council, ALF/LUA grants from the Sahlgrenska University Hospital. Declaration of Interests: Dr Axelsson has received lecture fees from Lilly, Meda/Mylan and Amgen. Prof Lorentzon has received lecture fees from Astellas, Amgen, Lilly, UCB Pharma, Radius Health, Meda/Mylan, GE-Lunar and Santax Medico/Hologic. Mr Litsne has no conflicts of interest. Ethics Approval Statement: The study was approved by the Swedish Ethical Review Authority.