title: Multiple imputation was an efficient method for harmonizing the Mini-Mental State Examination with missing item-level data.
abstract: OBJECTIVE
  The Mini-Mental State Examination (MMSE) is used to estimate current cognitive status and as a screen for possible dementia. Missing item-level data are commonly reported. Attention to missing data is particularly important. However, there are concerns that common procedures for dealing with missing data, for example, listwise deletion and mean item substitution, are inadequate.
  
  
  METHODS
  We used multiple imputation (MI) to estimate missing MMSE data in 17,303 participants who were drawn from the Dynamic Analyses to Optimize Aging project, a harmonization project of nine Australian longitudinal studies of aging.
  
  
  RESULTS
  Our results indicated differences in mean MMSE scores between those participants with and without missing data, a pattern consistent over age and gender levels. MI inflated MMSE scores, but differences between those imputed and those without missing data still existed. A simulation model supported the efficacy of MI to estimate missing item level, although serious decrements in estimation occurred when 50% or more of item-level data were missing, particularly for the oldest participants.
  
  
  CONCLUSIONS
  Our adaptation of MI to obtain a probable estimate for missing MMSE item level data provides a suitable method when the proportion of missing item-level data is not excessive.
authors.affiliation: Ageing Research Unit, Centre for Mental Health Research, Australian National University, Canberra, ACT, Australia. richard.burns@anu.edu.au
authors.forename: Richard A
authors.initials: RA
authors.lastname: Burns
authors.forename: Peter
authors.initials: P
authors.lastname: Butterworth
authors.forename: Kim M
authors.initials: KM
authors.lastname: Kiely
authors.forename: Allison A M
authors.initials: AA
authors.lastname: Bielak
authors.forename: Mary A
authors.initials: MA
authors.lastname: Luszcz
authors.forename: Paul
authors.initials: P
authors.lastname: Mitchell
authors.forename: Helen
authors.initials: H
authors.lastname: Christensen
authors.forename: Chwee
authors.initials: C
authors.lastname: Von Sanden
authors.forename: Kaarin J
authors.initials: KJ
authors.lastname: Anstey
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001315:Australia / Q000453:epidemiology; D003072:Cognition Disorders / Q000175:diagnosis* / Q000453:epidemiology; D003704:Dementia / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008609:Mental Status Schedule / Q000592:standards*; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D012737:Sex Factors