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Modeling Reserve as Residual Cognition Evidence That Lifetime Cognitive Activities Mediate the Reserve-Building Effects

Modeling Reserve as Residual Cognition Evidence That Lifetime Cognitive Activities Mediate the Reserve-Building Effects of Education. Maritza Dowling, Dan Mungas, Bruce Reed, Joshua Sonnen, Milton Strauss, Sarah Tomaszewski Farias. Background.

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Modeling Reserve as Residual Cognition Evidence That Lifetime Cognitive Activities Mediate the Reserve-Building Effects

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  1. Modeling Reserve as Residual CognitionEvidence That Lifetime Cognitive Activities Mediate the Reserve-Building Effects of Education Maritza Dowling, Dan Mungas, Bruce Reed, Joshua Sonnen, Milton Strauss, Sarah Tomaszewski Farias UC Davis Alzheimer’s Disease Center

  2. Background • Brain pathology diminishes cognitive performance; effects are highly variable across individuals • Cognitive reserve is often used to explain the imperfect correlation between brain pathology and clinical status • It is a hypothetical construct • Proxy variables, especially education, are often used in studies of cognitive reserve

  3. Approach • Conceptually, reserve explains deviations from the level of cognitive performance that would be expected for a given amount of brain pathology • High reserve = better than expected performance • We modeled reserve as residual cognition after accounting for neuropathology

  4. Npath 2 Npath 3 Npath 1 Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Conceptual Illustration of Approach ‘reserve’ Cognitive factor Residual

  5. Data Sources • 701 Neuropathology cases • Rush Memory Assessment Project (MAP) (n=272) • Rush Religious Orders Study (ROS)(n=429) • All cases had comparable annual neuropsychological assessments • Potential Reserve Indicators: leisure time cognitive activity (MAP), education, lifetime SES

  6. Model-building Steps paper #1, paper #2 • CFA of AD neuropathology • CFA of cognitive measures • Regression of cognitive domains (factors) on neuropathology (AD, VD, LBD) • Capture residual cognition in latent variables • Examine dimension structure of residuals across domains; create a second order reserve factor • Examine independent predictors of reserve

  7. A Model to Study the Determinants of Cognitive Reserve

  8. episR semR wmR ResComp pspR Educ porgR flR .11

  9. episR semR wmR ResComp pspR CogActBL CogAct40 Educ porgR flR LifeSES .28 .29 .35 -.20 .11

  10. Summary • It is possible to operationally define reserve as residual cognition using latent variable modeling • The 6 domain-specific measures of reserve were represented well by one global reserve construct. • Results consistent with previous studies from the Rush MAP showing that that have used cognitive activity as a proxy indicator of reserve • Unaware of any studies that examine how including cognitive activities modifies the effect of education on incident dementia or cognitive decline

  11. Prior papers suggest cognitive activities are particularly important markers of reserve, e.g. • Wilson 2002: Education effect becomes ns when CA are in model • Verghese 2003; Education and occupation effects are much weaker when CA are in model • Valenzuela 2005 review: Effect sizes in studies of CA on incident dementia are stronger than effects sizes of education or occupation. • Results are novel in showing that education is not positively related to reserve independent of cognitive activity • Unaware of any papers that have shown this reversal in the directionality of effect • Operationally defining reserve as residual cognition is a useful approach

  12. Next steps • More background investigation on reversal of education effect--would any further analyses clarify what is going on? • Otherwise, no more analysis needed • Draft Paper Quickly

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