Excess mortality following hip fracture: the role of underlying health status

Abstract

We evaluated the long-term excess mortality associated with hip fracture, using prospectively collected data on pre-fracture health and function from a nationally representative sample of U.S. elders. Although mortality was elevated for the first six months following hip fracture, we found no evidence of long-term excess mortality.

Introduction: The long-term excess mortality associated with hip fracture remains controversial.

Methods: To assess the association between hip fracture and mortality, we used prospectively collected data on pre-fracture health and function from a representative sample of U.S. elders in the Medicare Current Beneficiary Survey (MCBS) to perform survival analyses with time-varying covariates.

Results: Among 25,178 MCBS participants followed for a median duration of 3.8 years, 730 sustained a hip fracture during follow-up. Both early (within 6 months) and subsequent mortality showed significant elevations in models adjusted only for age, sex and race. With additional adjustment for pre-fracture health status, functional impairments, comorbid conditions and socioeconomic status, however, increased mortality was limited to the first six months after fracture (hazard ratio [HR]: 6.28, 95% CI: 4.82, 8.19). No increased mortality was evident during subsequent follow-up (HR: 1.04, 95% CI: 0.88, 1.23). Hip-fracture-attributable population mortality ranged from 0.5% at age 65 among men to 6% at age 85 among women.

Conclusions: Hip fracture was associated with substantially increased mortality, but much of the short-term risk and all of the long-term risk was explained by the greater frailty of those experiencing hip fracture.

Figure 1

Proportion of subjects at cohort entry with any limitations in Activities of Daily Living (ADLs) and Instrumental Activities of Daily Living (IADLs) and severity of impairment.

Figure 2

Hazard ratios and 95% confidence intervals for early (within 6 months) and late (beyond 6 months) mortality following hip fracture. Models 1, 2, and 3 include all subjects. Model 1 adjusts for age, sex, and race; Model 2 adjusts for age, sex, race, functional status, comorbid conditions and socioeconomic variables; Model 3 adjusts for age, sex, race, functional status, and comorbid conditions. Results for specified strata show hip fracture hazard ratios under Model 2.

Figure 3

Proportion of mortality in the population that is attributable to hip fracture by age and sex when adjustment is limited to age, sex and race (no health status adjustment) and when health status, and comorbid conditions are also included (health status adjustment). Error bars show upper 95% confidence interval.