title: Do physical activity, smoking, drinking, or depression modify transitions from cognitive impairment to functional disability?
abstract: BACKGROUND
  Individual-level modifiers can delay onset of limitations in basic activities of daily living (ADLs) among cognitively impaired individuals. We assessed whether these modifiers also delayed onset of limitations in instrumental ADLs (IADLs) among individuals at elevated dementia risk.
  
  
  OBJECTIVE
  To determine whether modifiable individual-level factors delay incident IADL limitations among adults stratified by dementia risk.
  
  
  METHODS
  Health and Retirement Study participants aged 65+ without activity limitations in 1998 or 2000 (n = 5,219) were interviewed biennially through 2010. Dementia probability, categorized in quartiles, was used to predict incident IADL limitations with Poisson regression. We estimated relative (risk ratio) and absolute (number of limitations) effects from models including dementia, individual-level modifiers (physical inactivity, smoking, no alcohol consumption, and depression) and interaction terms between dementia and individual-level modifiers.
  
  
  RESULTS
  Dementia probability quartile predicted incident IADL limitations (relative risk for highest versus lowest quartile = 0.44; 95% CI: 0.28-0.70). Most modifiers did not significantly increase risk of IADL limitations among the cognitively impaired. Physical inactivity (RR = 1.60; 95% CI: 1.16, 2.19) increased the risk of IADL limitations among the cognitively impaired. The interaction between physical inactivity and low dementia probability was statistically significant (p = 0.009) indicating that physical inactivity had significantly larger effects on incident IADLs among cognitively normal than among those with high dementia probability.
  
  
  CONCLUSIONS
  Physical activity may protect against IADL limitations while not smoking, alcohol consumption, and not being depressed do not afford substantial protection among the cognitively impaired. RESULTS highlight the need for extra support for IADLs among individuals with cognitive losses.
authors.affiliation: Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA Department of Social and Behavioral Sciences, Harvard School of Public Health, Boston, MA, USA Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Pamela M
authors.initials: PM
authors.lastname: Rist
authors.affiliation: Department of Social and Behavioral Sciences, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Jessica R
authors.initials: JR
authors.lastname: Marden
authors.affiliation: Division of Epidemiology and Community Health, School of Public Health, University of Minnesota, Minneapolis, MN, USA Minnesota Population Center, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Capistrant
authors.affiliation: Institute of Social Science Survey, Peking University, Peking, China.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Wu
authors.affiliation: Department of Social and Behavioral Sciences, Harvard School of Public Health, Boston, MA, USA Department of Epidemiology & Biostatistics, University of California, San Francisco, USA.
authors.forename: M Maria
authors.initials: MM
authors.lastname: Glymour
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000428:Alcohol Drinking / Q000453:epidemiology*; D003072:Cognition Disorders / Q000453:epidemiology / Q000503:physiopathology / Q000523:psychology; D015331:Cohort Studies; D003863:Depression / Q000453:epidemiology*; D006233:Persons with Disabilities / Q000523:psychology / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D009043:Motor Activity; D017063:Outcome Assessment, Health Care; D012907:Smoking / Q000453:epidemiology*
keywords: Cognition; disability; epidemiology