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Backgrounds: The relationship between kidney function and cognitive impairment in Parkinson's disease (PD) is poorly understood and underexplored. This study aims to explore whether renal indices can serve as indicators to monitor the cognitive impairment of PD., Methods: A total of 508 PD patients and 168 healthy controls from the Parkinson's Progression Markers Initiative (PPMI) were recruited, and 486 (95.7%) PD patients underwent longitudinal measurements. The renal indicators including serum creatinine (Scr), uric acid (UA), and urea nitrogen, as well as UA/Scr ratio and estimated glomerular filtration rate (eGFR), were measured. Cross-sectional and longitudinal associations between kidney function and cognitive impairment were evaluated using multivariable-adjusted models., Results: eGFR was associated with lower levels of cerebrospinal fluid (CSF) A β 1-42 ( p  = 0.0156) and α-synuclein ( p  = 0.0151) and higher serum NfL ( p  = 0.0215) in PD patients at baseline. Longitudinal results showed that decreased eGFR predicted a higher risk of cognitive impairment (HR = 0.7382, 95% CI = 0.6329-0.8610). Additionally, eGFR decline was significantly associated with higher rates of increase in CSF T-tau ( p  = 0.0096), P-tau ( p  = 0.0250), and serum NfL ( p  = 0.0189), as well as global cognition and various cognitive domains ( p  < 0.0500). The reduced UA/Scr ratio was also linked to higher NfL levels ( p  = 0.0282) and greater accumulation of T-tau ( p  = 0.0282) and P-tau ( p  = 0.0317). However, no significant associations were found between other renal indices and cognition., Conclusion: eGFR is altered in PD subjects with cognitive impairment, and predict larger progression of cognitive decline. It may assist identifying patients with PD at risk of rapid cognitive decline and have the potential to monitoring responses to therapy in future clinical practice., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Qu, Qin, Wang, Li, Zhao, An, Li, Mao, Min, Xiong and Xue.)

Backgrounds: Apathy is common in Parkinson's disease (PD) but difficult to identify. Growing evidence suggests that abnormal iron metabolism is associated with apathy in PD. We aimed to investigate the clinical features and iron metabolism of apathetic patients with PD, and construct a nomogram for predicting apathy in PD., Methods: Data of 201 patients with PD were analyzed. Demographic data, Apathy Scale (AS) assessments, and serum iron metabolism parameters were obtained. Spearman correlations were used to assess relationships between AS scores and iron metabolism parameters, separately for male and female patients. Additionally, a nomograph for detecting apathetic patients with PD was built based on the results of logistic regression analysis., Results: The serum transferrin (TRF, p  < 0.0024) concentration and total iron binding capacity (TIBC, p  < 0.0024) were lower in the apathetic group after Bonferroni correction, and they were negatively associated with AS scores in male participants with PD (TRF, r  = -0.27, p  = 0.010; TIBC, r  = -0.259, p  = 0.014). The nomogram was developed by incorporating the following five parameters: age, sex, serum iron concentration, TIBC and Hamilton Depression Rating Scale (HAMD) scores, which showed good discrimination and calibration, with a consistency index of 0.799 (95% confidence interval = 0.732-0.865)., Conclusion: Abnormal iron metabolism may contribute to apathy in PD, especially among men. TIBC levels in combination with HAMD scores can be effectively used for the prediction of apathetic patients with PD., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Li, Qu, Gao, Li, Qin, Wang, Zhao, Mao, Min, Xiong and Xue.)