The purpose of the current study was to evaluate the relationship between quantitative proteinuria (measured from 24-hour urine collections obtained 1993-1998) and mortality in chronic spinal cord injury (SCI) patients (n = 220) followed at the VAMC SCI center. Computerized medical records were reviewed in 2004 (follow-up period of 6-11 years) to determine overall mortality. Proteinuria was categorized as normal (< 150 mg, n = 31), microalbuminuria (150-300 mg, n = 70), or increasing degrees of proteinuria (0.3-0.5 g, n = 51; 0.5-1.0 g, n =3 7; > 1 g, n = 31). Long-term survival was assessed by Kaplan-Meier analysis. Regular and stepwise Cox proportional hazards models were used to determine risk factors for mortality. The dependent variable was duration of survival, in months. Independent variables assessed were proteinuria (mg/d), age, duration and type of injury, type of bladder management, ethnicity, diabetes mellitus, hypertension, coronary artery disease, hematocrit, creatinine clearance, and concentrations of albumin, creatinine, and cholesterol.
Results Increasing degrees of proteinuria were associated with decreased duration of survival, particularly in patients with > 1.0 g/d. Survival of patients with proteinuria < 1.0 g/d was significantly different from patients with > 1.0 g/d (log rank test, p < .0001). Patients with > 1.0 g/d proteinuria were significantly older, had longer duration of injury, higher serum creatinine concentrations, lower hematocrit, albumin, and creatinine clearance and were more likely to be paraplegic utilizing indwelling bladder catheters (p < .05). With stepwise Cox proportional hazards, the only statistically significant variable associated with increased mortality was ethnicity (African American with shorter duration of survival).
Conclusion Proteinuria (> 1 g/d) is associated with decreased survival and impaired log-term renal function, whereas levels of proteinuria associated with microalbuminuria in the general population (150-300 mg/d) were not associated with increased mortality in the SCI population.