title: Cumulative impact of health deficits, social vulnerabilities, and protective factors on cognitive dynamics in late life: a multistate modeling approach.
abstract: BACKGROUND
  Many factors influence late-life cognitive changes, and evaluating their joint impact is challenging. Typical approaches focus on average decline and a small number of factors. We used multistate transition models and index variables to look at changes in cognition in relation to frailty (accumulation of health deficits), social vulnerability, and protective factors in the Honolulu-Asia Aging Study (HAAS).
  
  
  METHODS
  The HAAS is a prospective cohort study of 3,845 men of Japanese descent, aged 71 to 93 years at baseline. Cognitive function was measured using the Cognitive Abilities Screening Instrument (CASI). Baseline index variables were constructed of health deficits (frailty), social vulnerabilities, and protective factors. The chances of improvement/stability/decline in cognitive function and death were simultaneously estimated using multistate transition modeling for 3- and 6-year transitions from baseline.
  
  
  RESULTS
  On average, CASI scores declined by 5.3 points (standard deviation (SD) = 10.0) over 3 years and 9.5 points (SD = 13.9) over 6 years. After adjusting for education and age, baseline frailty was associated with an increased risk of cognitive decline at 3 years (β = 0.18, 95% confidence interval (CI), 0.08 to 0.29) and 6 years (β = 0.40, 95% CI, 0.27 to 0.54). The social vulnerability index was associated with 3-year changes (β = 0.16, 95% CI, 0.09 to 0.23) and 6-year changes (β = 0.14, 95% CI, 0.05 to 0.24) in CASI scores. The protective index was associated with reductions in cognitive decline over the two intervals (3-year: β = -0.16, 95% CI, -0.24 to -0.09; 6-year: β = -0.21, 95% CI, -0.31 to -0.11,).
  
  
  CONCLUSIONS
  Research on cognition in late life needs to consider overall health, the accumulation of protective factors, and the dynamics of cognitive change. Index variables and multistate transition models can enhance understanding of the multifactorial nature of late-life changes in cognition.
authors.affiliation: Geriatric Medicine Research, Faculty of Medicine, Dalhousie University, Halifax, NS Canada.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Armstrong
authors.affiliation: Geriatric Medicine Research, Faculty of Medicine, Dalhousie University, Halifax, NS Canada.
authors.forename: Arnold
authors.initials: A
authors.lastname: Mitnitski
authors.affiliation: Geriatric Medicine Research, Faculty of Medicine, Dalhousie University, Halifax, NS Canada ; Department of Medicine, Division of Geriatric Medicine, Dalhousie University, Halifax, NS Canada.
authors.forename: Melissa K
authors.initials: MK
authors.lastname: Andrew
authors.affiliation: Laboratory of Epidemiology, Demography, and Biometry, National Institute on Aging, Bethesda, MD USA.
authors.forename: Lenore J
authors.initials: LJ
authors.lastname: Launer
authors.affiliation: Pacific Health Research & Education Institute, Honolulu, HI USA.
authors.forename: Lon R
authors.initials: LR
authors.lastname: White
authors.affiliation: Geriatric Medicine Research, Faculty of Medicine, Dalhousie University, Halifax, NS Canada ; Department of Medicine, Division of Geriatric Medicine, Dalhousie University, Halifax, NS Canada.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Rockwood