Additive effect of age on disability for individuals with spinal cord injuries

Abstract

Objective: To examine the additive effect of age on disability for adults with spinal cord injury (SCI).

Design: Prospective cohort study.

Setting: SCI Model Systems.

Participants: Individuals with SCI (median age at injury, 32 y; range, 6-88 y) with a discharge motor FIM score and at least 1 follow-up motor FIM score who also provided measures of other covariates (N=1660). Of the total sample, 79% were men, 72% were white, 16% had incomplete paraplegia, 33% had complete paraplegia, 30% had incomplete tetraplegia, and 21% had complete tetraplegia.

Interventions: Not applicable.

Main outcome measures: The primary study outcome was the motor subscale of the FIM. A mixed-models approach was used to examine the additive effect of age on disability for individuals with SCI.

Results: When controlling for motor FIM at discharge from rehabilitation, level and severity of injury, age at injury, sex, race, and the age × time interaction were not significant (P=.07). Age at the time of SCI was significantly associated with motor FIM (F1,238=22.49, P<.001). Two sensitivity analyses found significant interactions for both age × time (P=.03, P=.02) and age × time-square (P=.01, P=.006) models. Trajectory of motor FIM scores is moderated slightly by age at the time of injury. The older participants were at the time of injury, the greater the curvature and the more rapid decline were found in later years.

Conclusions: These findings indicate that age moderately influences disability for some individuals with SCI: the older the age at the time of injury, the greater the influence age has on disability. The findings serve as an important empirical foundation for the evaluation and development of interventions designed to augment accelerated aging experienced by individuals with SCI.

Keywords: Aging; Rehabilitation; Spinal cord injuries.