The risk of Parkinson's disease according to diabetic kidney disease status in a Korean population

Introduction: Type 2 diabetes is a risk factor for Parkinson's disease (PD). Recently, it has been reported that proteinuria without reduced estimated glomerular filtration rate (eGFR) can increase the risk of PD development. The objective of this study was to evaluate the risk of PD among Korean adults with type 2 diabetes stratified by proteinuria (PU) and eGFR levels. Methods: Using the Korean National Health Insurance Service database, a total of 2,217,326 patients with type 2 diabetes who underwent regular health check-ups from 2009 to 2012 were included. These patients were classified into four groups (no-diabetic kidney disease (DKD) (PU⁻GFR^-), proteinuric DKD with normal eGFR (PU⁺GFR⁻), nonproteinuric DKD (PU⁻GFR⁺), and proteinuric DKD with reduced eGFR (PU⁺GFR⁺) and followed up until 2018. PD was defined using International Classification of Diseases, 10th revision. Results: The prevalence of PU⁻GFR^-, PU⁺GFR⁻, PU⁻GFR⁺, or PU⁺GFR⁺ phenotype was 83.3%, 5.0%, 10.1%, or 1.6%, respectively. During a median follow-up of 7.2 years, 16,079 participants developed PD. Hazard ratios for PD were 1.10 (95% confidence interval [CI]: 1.01–1.21, p = 0.0091), 1.15 (95% CI: 1.09–1.21, p < 0.0001), and 1.23 (95% CI: 1.09–1.39, p < 0.0001) for participants in PU⁺GFR⁻, PU⁻GFR⁺, and PU⁺GFR⁺ groups relative to those in the PU⁻GFR^- group, respectively. Effects of DKD on PD were more pronounced in those aged less than 65 years. Conclusion: Reduced eGFR and/or proteinuria might be independent risk factors for boosting PD development among patients with type 2 diabetes. More attention should be paid to PD in patients with DKD, even in a younger aged population.