Identification of inverted U-shaped curve association between serum potassium and prodromal Parkinson's disease.

Background: The association between serum potassium and prodromal Parkinson's disease (PPD) remains unclear currently. Objective: The ultimate goal is to gain a deeper understanding of the implications of this association between serum potassium and PPD. Methods: We conducted a retrospective cross-sectional study involving 1035 participants in PPMI cohort. Age, sex, education years, race, body mass index (BMI), calcium, alanine aminotransferase, aspartate aminotransferase, lymphocytes, neutrophils, serum uric acid, serum sodium, serum potassium, creatinine, serum glucose were obtained from all participants. Logistic regression, and smooth curve fitting were utilized to substantiate the research objectives. Results: The overall PPD was 83.4 % (863/1035). Multivariate odds ratio regression adjusted for risk factors demonstrates a 1-unit increment in the serum potassium raises the risk of PPD by 1.82 times, respectively. Smooth splines analysis suggested an inverted U-shaped association between serum potassium and PPD (P nonlinearity < 0.05), with the zenith of risk at 4.479 mmol/L. Further subgroup analysis and sensitivity analyses supported the primary findings and indicated the conclusions are robust. Conclusions: This study highlights the association between serum potassium levels and the risk of incident PPD, independent of confounders. The association between serum potassium and PPD is inverted U-shaped, the threshold value is 4.479 mmol/l.