title: Functional status in the young-old: establishing a working prototype of an extended-instrumental activities of daily living scale.
abstract: BACKGROUND
  Instrumental activities of daily living (IADLs) exhibit strong predictive power for the presence of dementia and mild cognitive impairment. However, IADLs are often less effective in younger cohorts or in healthy community-dwelling samples, presenting with large ceiling effects. This study aimed to construct an IADL scale with an extended range. An effort was made to incorporate leisure activity tasks that were more stimulating, and potentially more challenging, into a set of traditional IADLs.
  
  
  METHODS
  Beginning with a set of IADL and leisure activity items, nonparametric item response theory methodology was used to construct a scale with appropriate dimensionality, monotonicity, item discrimination power, and scalability within a large cohort of young-old (aged 65-75). Dimensionality was further scrutinized by principal component analysis of the residuals. The predictive validity of the resulting scale for poor cognitive performance was evaluated using logistic regression.
  
  
  RESULTS
  A reliable (ρ = .73) unidimensional construct was established, meeting the Mokken item response theory criteria of medium scalability. Excluding demented participants, the adjusted model proved sensitive to relatively subtle cognitive deficits; each additional task endorsed (nine-item scale) significantly decreased the odds of being in the bottom quarter of composite domains relating to processing speed (odds ratio = 0.73 [confidence interval: 0.56-0.97], p < .05) and visuospatial ability (odds ratio = 0.70 [confidence interval: 0.73-0.87], p < .01).
  
  
  CONCLUSIONS
  A reliable extended-IADL scale was constructed meeting item response theory assumptions relating to unidimensionality, monotonicity, and invariant item ordering. The range of measurement extends well beyond traditional IADL scales. Finally, the scale appears to be sensitive to cognitive differences within the normal spectrum.
authors.affiliation: Cognitive Neuroscience Division, Department of Neurology and Taub Institute and.
authors.forename: Robert
authors.initials: R
authors.lastname: Fieo
authors.affiliation: Cognitive Neuroscience Division, Department of Neurology and Taub Institute and.
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Manly
authors.affiliation: The Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University College of Physicians and Surgeons, New York.
authors.forename: Nicole
authors.initials: N
authors.lastname: Schupf
authors.affiliation: Cognitive Neuroscience Division, Department of Neurology and Taub Institute and ys11@columbia.edu.
authors.forename: Yaakov
authors.initials: Y
authors.lastname: Stern
mesh_terms: D000203:Activities of Daily Living / Q000523:psychology*; D000368:Aged; D000375:Aging; D003071:Cognition / Q000502:physiology*; D060825:Cognitive Dysfunction / Q000503:physiopathology* / Q000523:psychology / Q000534:rehabilitation; D004185:Disability Evaluation; D005500:Follow-Up Studies; D006801:Humans; D007899:Leisure Activities / Q000523:psychology*; D009043:Motor Activity / Q000502:physiology*; D011379:Prognosis; D012189:Retrospective Studies
keywords: Cognitive aging; Functional performance; Successful aging.