Date

June 2008

Document Type

Dissertation

Degree Name

Ph.D.

Institution

Oregon Health & Science University

Abstract

Introduction Traumatic injury is the seventh leading cause of death in the geriatric population. High in-hospital case fatality rates have been well documented yet little is known about the long-term effects of injury on seniors who survive to trauma center discharge. Previous investigations have identified an ongoing mortality risk in the months and years following injury but few have compared subjects’ mortality rates to population-based norms. Aim 1 of this study was to quantify the influence of injury on geriatric patients’ five-year survival, compared to each patient’s projected life expectancy, based on actuarial norms. A second aim was to examine the relationship between five-year survival and various patient and injury characteristics, present at the time of hospital discharge, in order to identify variables associated with increased risk of death. Methods The primary data source for this retrospective, population-based cohort design study was all patients entered into the Oregon Trauma Registry between 1992 and 2000, who were 65 years of age or older at the time of injury, and who were discharged alive. Subjects’ records were cross-linked with the National Death Index to ascertain vital status and age at death. Total sample size was 3,633. For the 1,970 subjects injured between 1997 and 2000, expected age at death was determined by assigning hypothetical, age, race, and gender matched controls derived from the U.S. Life Tables. For Aim 1, Cox proportional hazards model was used to determine hazard ratios for death in 1,970 subjects versus controls within five years of injury. For Aim 2, all 3,633 subjects were entered into bivariate and multivariate Cox proportional hazards models to identify pre-injury, injury, and post-injury variables associated with life expectancy in geriatric trauma survivors. Results The all cause hazard for death in injured subjects was 6.26 times that of controls (males 7.42, females 5.31). Of the pre-injury, injury, and post-injury variables tested, only gender, age at the time of injury, preexisting systems dysfunction, location of injury occurrence, discharge disposition, and discharge limitations score predicted five-year vital status in the final, multivariate model. Injury Severity Scores did not predict longterm survival. Compared to those injured on roadways, persons injured in a residential institution had a hazard ratio of 3.07; those injured at farm/logging/industrial sites experienced a hazard ratio of 0.48. Compared to a home discharge location, the 5-year mortality hazard for subjects discharged to a skilled nursing facility was 1.24; 1.68 for those discharged to an acute care facility. Discussion This was the first large-scale study to employ actuarial data to identify the increased long-term burden of mortality on geriatric trauma survivors—across all injury types, mechanisms, and severities—in order to provide a comprehensive perspective of post-trauma outcomes in a state with an inclusive and well-established trauma system. Two key findings were evident. There is a quantifiable, ongoing, long-term (five year) relationship between trauma and shortened lifespan in geriatric Oregon Trauma Registry survivors. The second key finding was that this long-term relationship between trauma and death is largely influenced by host factors (pre- and post-injury patient status), rather than by factors directly associated with the injuring event.

Identifier

doi:10.6083/M49P2ZMX

School

School of Nursing

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