title: Social Markers of Mild Cognitive Impairment: Proportion of Word Counts in Free Conversational Speech.
abstract: BACKGROUND
  Detecting early signs of Alzheimer's disease (AD) and mild cognitive impairment (MCI) during the pre-symptomatic phase is becoming increasingly important for costeffective clinical trials and also for deriving maximum benefit from currently available treatment strategies. However, distinguishing early signs of MCI from normal cognitive aging is difficult. Biomarkers have been extensively examined as early indicators of the pathological process for AD, but assessing these biomarkers is expensive and challenging to apply widely among pre-symptomatic community dwelling older adults. Here we propose assessment of social markers, which could provide an alternative or complementary and ecologically valid strategy for identifying the pre-symptomatic phase leading to MCI and AD.
  
  
  METHODS
  The data came from a larger randomized controlled clinical trial (RCT), where we examined whether daily conversational interactions using remote video telecommunications software could improve cognitive functions of older adult participants. We assessed the proportion of words generated by participants out of total words produced by both participants and staff interviewers using transcribed conversations during the intervention trial as an indicator of how two people (participants and interviewers) interact with each other in one-on-one conversations. We examined whether the proportion differed between those with intact cognition and MCI, using first, generalized estimating equations with the proportion as outcome, and second, logistic regression models with cognitive status as outcome in order to estimate the area under ROC curve (ROC AUC).
  
  
  RESULTS
  Compared to those with normal cognitive function, MCI participants generated a greater proportion of words out of the total number of words during the timed conversation sessions (p=0.01). This difference remained after controlling for participant age, gender, interviewer and time of assessment (p=0.03). The logistic regression models showed the ROC AUC of identifying MCI (vs. normals) was 0.71 (95% Confidence Interval: 0.54 - 0.89) when average proportion of word counts spoken by subjects was included univariately into the model.
  
  
  CONCLUSIONS
  An ecologically valid social marker such as the proportion of spoken words produced during spontaneous conversations may be sensitive to transitions from normal cognition to MCI.
authors.affiliation: Mail Code CR131, 3181 SW Sam Jackson Park Rd, Department of Neurology, Oregon Health & Science University, Portland, OR 97239-3098, USA. Hdodge@med.umich.edu.
authors.forename: Hiroko H
authors.initials: HH
authors.lastname: Dodge
authors.forename: Nora
authors.initials: N
authors.lastname: Mattek
authors.forename: Mattie
authors.initials: M
authors.lastname: Gregor
authors.forename: Molly
authors.initials: M
authors.lastname: Bowman
authors.forename: Adriana
authors.initials: A
authors.lastname: Seelye
authors.forename: Oscar
authors.initials: O
authors.lastname: Ybarra
authors.forename: Meysam
authors.initials: M
authors.lastname: Asgari
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Kaye
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000523:psychology / Q000534:rehabilitation; D058070:Asymptomatic Diseases / Q000534:rehabilitation; D015415:Biomarkers; D060825:Cognitive Dysfunction / Q000523:psychology* / Q000534:rehabilitation*; D018450:Disease Progression; D005260:Female; D006801:Humans; D007406:Interview, Psychological / Q000379:methods*; D016015:Logistic Models; D008297:Male; D009483:Neuropsychological Tests; D012919:Social Behavior; D013060:Speech / Q000502:physiology*
chemical_list: D015415:Biomarkers