title: Speed of processing and depression affect function in older adults with mild cognitive impairment.
abstract: OBJECTIVE
  To evaluate the effect of depression and cognition on function in older adults with amnestic and nonamnestic mild cognitive impairment (aMCI and nonaMCI).
  
  
  METHODS
  The study uses baseline data from the National Alzheimer's Coordinating Center.
  
  
  METHODS
  Data were collected at multiple Alzheimer's Disease Centers in the United States.
  
  
  METHODS
  The sample included a total of 3,117 individuals with MCI, mean age = 74.37 years, SD: 9.37 (aMCI, n = 2,488; non-aMCI, n = 629).
  
  
  METHODS
  The 10-item Pfeffer Functional Activities Questionnaire assessed function.
  
  
  RESULTS
  Depressive symptoms (Geriatric Depression Scale), memory impairment (Logical Memory II), and processing speed decrements (Digit Symbol Substitution Test) were significantly associated with functional impairment (p <0.001). Processing speed partially mediated the effect of depression on function and fully mediated the effect of executive dysfunction on function (p <0.001) in the total MCI and aMCI subsample, while in the non-aMCI subsample, processing speed mediated the effect of executive function but not the effect of depression (p = 0.20) on function.
  
  
  CONCLUSIONS
  The findings show that processing speed is central to the effect that depression and executive dysfunction have on functional impairment in cognitively impaired older adults. Future studies are needed to better understand the physiologic underpinnings in age-related and disease-specific decrements in processing speed, and to address the problems in the assessment of processing speed in clinical samples.
authors.affiliation: Columbia University College of Physicians and Surgeons and New York State Psychiatric Institute, New York, NY 10032, USA. pb2410@columbia.edu
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Brown
authors.forename: Xinhua
authors.initials: X
authors.lastname: Liu
authors.forename: Joel R
authors.initials: JR
authors.lastname: Sneed
authors.forename: Monique A
authors.initials: MA
authors.lastname: Pimontel
authors.forename: D P
authors.initials: DP
authors.lastname: Devanand
authors.forename: Steven P
authors.initials: SP
authors.lastname: Roose
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D060825:Cognitive Dysfunction / Q000523:psychology*; D003866:Depressive Disorder / Q000523:psychology*; D056344:Executive Function; D005163:Factor Analysis, Statistical; D005260:Female; D015577:Geriatric Assessment; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D012044:Regression Analysis; D011795:Surveys and Questionnaires