Long-term disability and survival in traumatic brain injury: results from the National Institute on Disability and Rehabilitation Research Model Systems

Abstract

Objectives: To document long-term survival in 1-year survivors of traumatic brain injury (TBI); to compare the use of the Disability Rating Scale (DRS) and FIM as factors in the estimation of survival probabilities; and to investigate the effect of time since injury and secular trends in mortality.

Design: Cohort study of 1-year survivors of TBI followed up to 20 years postinjury. Statistical methods include standardized mortality ratio, Kaplan-Meier survival curve, proportional hazards regression, and person-year logistic regression.

Setting: Postdischarge from rehabilitation units.

Participants: Population-based sample of persons (N=7228) who were admitted to a TBI Model Systems facility and survived at least 1 year postinjury. These persons contributed 32,505 person-years, with 537 deaths, over the 1989 to 2011 study period.

Interventions: Not applicable.

Main outcome measure: Survival.

Results: Survival was poorer than that of the general population (standardized mortality ratio=2.1; 95% confidence interval, 1.9-2.3). Age, sex, and functional disability were significant risk factors for mortality (P<.001). FIM- and DRS-based proportional hazards survival models had comparable predictive performance (C index: .80 vs .80; Akaike information criterion: 11,005 vs 11,015). Time since injury and current calendar year were not significant predictors of long-term survival (both P>.05).

Conclusions: Long-term survival prognosis in TBI depends on age, sex, and disability. FIM and DRS are useful prognostic measures with comparable statistical performance. Age- and disability-specific mortality rates in TBI have not declined over the last 20 years. A survival prognosis calculator is available online (http://www.LifeExpectancy.org/tbims.shtml).

Keywords: AIC; Akaike information criterion; Brain injuries; CI; DRS; Disability Rating Scale; Mortality; Rehabilitation; SMR; SSDI; Social Security Death Index; Survival; TBI; confidence interval; standardized mortality ratio; traumatic brain injury.