Ageing with spinal cord injury: cross-sectional and longitudinal effects

Study design: Longitudinal and cross-sectional. Objective: To determine whether, for studies of ageing with a spinal cord injury, the cross-sectional differences in outcomes across both age and years post injury (YPI) differ from the longitudinal change. Setting: Two SCI centres in England: the National Spinal Injuries Centre in Aylesbury, and the Regional Spinal Injuries Centre in Southport. Methods: A total of 315 people who sustained spinal cord injuries prior to 1971 underwent comprehensive health and psychosocial status interviews at one or more of the study assessments (1990, 1993, 1996, and 1999). A range of continuous and dichotomous outcomes was analyzed to detect both cross-sectional differences by age and average individual changes over multiple measurements. Results: Frequently, outcomes changed longitudinally without showing any cross-sectional differences. Cross-sectional age was more commonly associated with the worsening of a condition while cross-sectional YPI was commonly associated with improvement. After controlling for cross-sectional effects, psychological measures generally showed minor deterioration, measures of community integration both improved and deteriorated, upper extremity pain increased, lower enxtremity pain decreased, and participants tended to quit smoking. Conclusion: Using longitudinal findings that control for cross-sectional differences produces a more complete description of ageing with a spinal cord injury.