Understanding age effects associated with changes in secondary health conditions in a Canadian spinal cord injury cohort

Study design: Longitudinal cohort. Objectives: To determine whether changes in secondary health conditions (SHC) associated with spinal cord injury (SCI) were effectively modeled from a longitudinal or cross-sectional perspective, and whether the changes in SHCs were attributable to age or years post-injury (YPI). Setting: Toronto Rehabilitation Institute, Lyndhurst Centre. Methods: Telephone survey methods were used to collect data on (1) demographics, (2) impairment, (3) health status, and (4) self-reported SHCs at two time intervals (1995-1997; 2003-2004) from 344 adults with SCI. Generalized estimating equations were applied to model the longitudinal and cross-sectional effects. Results: Health status decreased over time (P<0.0005), whereas the number of SHCs increased (P<0.0001). Regardless of age or YPI, the longitudinal component of aging better predicted SHC occurrence and was associated with spasticity [odds ratio, OR = 1.055 (95% confidence interval, CI, 1.018 to 1.093, P<0.01)], kidney problems [OR = 1.154 (95% CI, 1.084 to 1.229, P<0.0001)], cardiac problems [OR = 1.168 (95% CI, 1.060 to 1.286, P<0.01)], high blood pressure [OR = 1.121 (95% CI, 1.058 to 1.188, P<0.0001)], chronic pain [OR = 1.058 (95% CI, 1.021 to 1.096, P<0.01)], and arthritis/joint pain [OR = 1.113 (95% CI, 1.075 to 1.152, P<0.0001)]. Conclusion: Within a relatively short period of time, persons with SCI experienced substantive declines in health. The findings suggest that a longitudinal perspective is more sensitive for predicting the risk of self-reported SHCs than a cross-sectional one. Spinal Cord (2010) 48, 330-335; doi: 10.1038/sc.2009.135; published online 13 October 2009