Seasonal Variation in Hip Fracture Mortality

OBJECTIVES: This study aims to identify if wintertime surgery increases the mortality of the patients after hip fracture operations. DESIGN: Retrospective observational cohort study. SETTING: The data for this citywide retrospective observational cohort study came from Clinical Data Analysis Reporting System. PATIENT: This study included 35 409 patients with hip fracture operations from July 2005 to December 2013. MAIN OUTCOME MEASURES: Cox regression hazard model was used to estimate the independent effect of operation being performed in winter on the hazard of mortality. The hazard model included covariates found to be independent predictors of mortality: age, sex, surgical delay, and Charlson Comorbidity Index (CCI). RESULTS: There was a seasonal variation with more hip fracture operations happening in the winter months. The 1-month, 6-month, 1-year, and 5-year mortality were 3%, 11%, 17%, and 47%, respectively. Operation performed in winter was associated with a higher hazard of mortality (hazard ratio [HR] 1.040; 95% confidence interval: 1.010-1.072; P = .009). The HR was greater with male sex (HR 1.786; P = .000), advanced age (≥85 years old: HR 2.819; P = .000), the longer surgical delay (HR 1.018; P = .000), and higher CCI (severe CCI group: HR 2.963; P = .000). CONCLUSION: Wintertime hip fracture surgery was associated with an increased hazard of mortality after adjusting for other known risk factors affecting mortality post hip fracture operations.