Longitudinal cohort. 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). Toronto Rehabilitation Institute, Lyndhurst Centre. 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. 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)]. 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.
