Statistical analyses were conducted using the software programs R version 4.0.3 (R Foundation for Statistical Computing, Vienna, Austria) and a graphical interface EZR (Saitama Medical Center, Jichi Medical University, Saitama, Japan)27 (link) or GraphPad Prism version 9 (GraphPad Software, San Diego, CA). Missing data were handled using pairwise deletion approach. Categorical variables are presented as percentages, and differences between groups were evaluated using the Fisher exact test. Post hoc analyses for multiple comparison were performed using Bonferroni correction. Continuous variables are presented as mean ± SD. Differences between groups were evaluated using the Welch t test or one-way analysis of variance followed by post hoc analyses using the Tukey test. Analysis of covariance (ANCOVA) was performed to evaluate the difference of CSF p-tau181 between NIID and disease controls using CSF t-tau as a covariate, after confirming the correlation between CSF p-tau181 and t-tau in each group. Pearson correlation analysis was conducted between CSF p-tau181 and other continuous variables in patients with NIID. Multivariate analysis was not conducted due to a limited number of patients with NIID. p Values of <0.05 were considered statistically significant for all analyses.