Kidney Disease as a Predictor of Mortality in Chronic Spinal Cord Injury

Background

The purpose of this study is to assess the predictive value of proteinuria and creatinine clearance (CrCl) in relation to mortality in patients with spinal cord injury.

Methods

Computerized medical records covering 6 to 11 years were reviewed in 2004 to determine all-cause mortality. Long-term survival was assessed by means of Kaplan-Meier analysis. Multiple and stepwise Cox proportional hazards models were used to identify risk factors for mortality. The dependent variable was duration of survival in months. Potential predictors included proteinuria, CrCl, age, duration and type of injury, type of bladder management, ethnicity, diabetes mellitus, hypertension, coronary artery disease, hematocrit, serum albumin level, and serum cholesterol level.

Results

With the Cox model, proteinuria with protein of 500 mg/d or greater (hazard ratio [HR], 2.98), CrCl less than 60 mL/min (<1.00 mL/s; HR, 3.89), or both (HR, 7.86) were associated independently with increased mortality. When added individually to the base Cox model, bladder catheter use (HR, 1.70) and age (HR, 1.05) also were independently predictive of time to death. Patients with preserved CrCl (≥60 mL/min) and no proteinuria (protein < 500 mg/d) had a significantly greater duration of survival compared with patients with proteinuria (protein ≥ 500 mg/d), decreased CrCl (<60 mL/min), or both (median survival, 120, 86, 87, and 47 months, respectively; P < 0.0001). There was no significant difference in survival in patients with proteinuria (protein ≥ 500 mg/d) and preserved CrCl (≥60 mL/min) compared with those with no proteinuria (protein < 500 mg/d) and decreased CrCl (<60 mL/min; P = 0.90). However, those with both proteinuria and decreased CrCl had significantly worse survival compared with those with only 1 condition (P < 0.01). Kidney disease was associated with an increase in both cardiovascular and noncardiovascular mortality.

Conclusion

The presence of either proteinuria with protein of 500 mg/d or greater or CrCl less than 60 mL/min is associated independently with increased mortality in the chronic spinal cord injury population. The presence of both conditions further increases this risk.

Index Words: Proteinuria, creatinine clearance, chronic kidney disease (CKD), mortality, spinal cord injury