Effect Modification on Death by Age and Sex in Elderly Hip Fracture

BACKGROUND: This study compared the effects of hip fractures on mortality according to sex and age in a nationwide cohort of elderly patients with hip fractures and controls. METHODS: Patients with hip fractures and matched controls were selected from the National Health Insurance Service-Senior cohort. Time-dependent propensity score matching was estimated from a Cox proportional hazards model with January 1, 2005, as the baseline and hip fracture as an event. Patients were matched by age and sex to participants at risk of developing a hip fracture at time zero. The effect size is presented as hazard ratio (HR) using a Cox proportional hazards model with a robust variance estimator that accounts for clustering within the matched pairs. RESULTS: Altogether, 14,283 patients with incident hip fractures and 28,566 matched controls were identified. The HR of male sex in hip fractures was 1.31 (95% confidence interval [CI], 1.22–1.40; P(interaction)<0.01). Moreover, the HR of age group in hip fractures was 0.73 (95% CI, 0.66–0.80; P(interaction)< 0.01) between the 65 to 74 and 75 to 84 years groups, 0.76 (95% CI, 0.71–0.81; P(interaction)< 0.01) between the 75 to 84 and ≥85 years groups, and 0.55 (95% CI, 0.50–0.61; P(interaction)< 0.01) between the 65 to 74 and ≥85 years groups. CONCLUSIONS: Male sex increases the risk of death in elderly patients with hip fractures versus matched controls, but the increased risk of death with age in hip fractures was decreased compared to that in matched controls.