Development and validation of the dialysis dementia risk score: A retrospective, population-based, nested case-control study.

BACKGROUND Dementia is prevalent and underdiagnosed in the dialysis population. We aimed to develop and validate a simple dialysis dementia scoring system to facilitate identification of individuals who are at high risk for dementia. METHODS We applied a retrospective, nested case-control study design using a national dialysis cohort derived from the National Health Insurance Research Database in Taiwan. Patients aged between 40 and 80 years were included and 2940 patients with incident dementia were matched to 29,248 non-dementia controls. All subjects were randomly divided into the derivation and validation sets with a ratio of 4:1. Conditional logistic regression models were used to identify factors contributing to the risk score. The cutoff value of the risk score was determined by Youden's J statistic and the graphic method. RESULTS The dialysis dementia risk score (DDRS) finally included age and 10 comorbidities as risk predictors. The C-statistic of the model was 0.71 (95% confidence interval [CI] 0.70-0.72). Calibration revealed a strong linear relationship between predicted and observed dementia risk (R2  = 0.99). At a cutoff value of 50 points, the high-risk patients had an approximately three-fold increased risk of having dementia compared to those with low risk (odds ratio [OR] 3.03, 95% CI 2.78-3.31). The DDRS performance, including discrimination (C-statistic 0.71, 95% CI 0.69-0.73) and calibration (p value of Hosmer-Lemeshow test for goodness of fit = 0.18), was acceptable during validation. The OR value (2.82, 95% CI 2.37-3.35) was similar to those in the derivation set. CONCLUSION The DDRS system has the potential to serve as an easily accessible screening tool to determine the high-risk groups who deserve subsequent neurological evaluation in daily clinical practice.