COVID-19 during the index hospital admission confers a 'double-hit' effect on hip fracture patients and is associated with a two-fold increase in 1-year mortality risk.

Purpose: The aims were to: (1) determine 1-year mortality rates for hip fracture patients during the first UK COVID-19 wave, and (2) assess mortality risk associated with COVID-19.

Methods: A nationwide multicentre cohort study was conducted of all patients presenting to 17 hospitals in March-April 2020. Follow-up data were collected one year after initial hip fracture ('index') admission, including: COVID-19 status, readmissions, mortality, and cause of death.

Results: Data were available for 788/833 (94.6%) patients. One-year mortality was 242/788 (30.7%), and the prevalence of COVID-19 within 365 days of admission was 142/788 (18.0%). One-year mortality was higher for patients with COVID-19 (46.5% vs. 27.2%; p < 0.001), and highest for those COVID-positive during index admission versus after discharge (54.7% vs. 39.7%; p = 0.025). Anytime COVID-19 was independently associated with 50% increased mortality risk within a year of injury (HR 1.50, p = 0.006); adjusted mortality risk doubled (HR 2.03, p < 0.001) for patients COVID-positive during index admission. No independent association was observed between mortality risk and COVID-19 diagnosed following discharge (HR 1.16, p = 0.462). Most deaths (56/66; 84.8%) in COVID-positive patients occurred within 30 days of COVID-19 diagnosis (median 11.0 days). Most cases diagnosed following discharge from the admission hospital occurred in downstream hospitals.

Conclusion: Almost half the patients that had COVID-19 within 365 days of fracture had died within one year of injury versus 27.2% of COVID-negative patients. Only COVID-19 diagnosed during the index admission was associated independently with an increased likelihood of death, indicating that infection during this time may represent a 'double-hit' insult, and most COVID-related deaths occurred within 30 days of diagnosis.