title: Using quantile regression to create baseline norms for neuropsychological tests.
abstract: BACKGROUND
  The Uniform Data Set (UDS) contains neuropsychological test scores and demographic information for participants at Alzheimer's disease centers across the United States funded by the National Institute on Aging. Mean regression analysis of neuropsychological tests has been proposed to detect cognitive decline, but the approach requires stringent assumptions.
  
  
  METHODS
  We propose using quantile regression to directly model conditional percentiles of neuropsychological test scores. An online application allows users to easily implement the proposed method.
  
  
  RESULTS
  Scores from 13 different neuropsychological tests were analyzed for 5413 cognitively normal participants in the UDS. Quantile and mean regression models were fit using age, gender, and years of education. Differences between the mean and quantile regression estimates were found on the individual measures.
  
  
  CONCLUSIONS
  Quantile regression provides more robust estimates of baseline percentiles for cognitively normal adults. This can then serve as standards against which to detect individual cognitive decline.
authors.affiliation: Department of Biostatistics, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Ben
authors.initials: B
authors.lastname: Sherwood
authors.affiliation: Department of Biostatistics, University of Washington, Seattle, WA, USA.
authors.forename: Andrew Xiao-Hua
authors.initials: AX
authors.lastname: Zhou
authors.affiliation: Department of Psychiatry and Behavioral Sciences and Neurology - Ken and Ruth Davee Department, Northwestern University, Chicago, IL, USA.
authors.forename: Sandra
authors.initials: S
authors.lastname: Weintraub
authors.affiliation: School of Statistics, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Lan
authors.initials: L
authors.lastname: Wang
keywords: Alzheimer's disease; Cognitive decline; Early detection; Neuropsychological assessment; Quantile regression