title: Assessment of complex mental activity across the lifespan: development of the Lifetime of Experiences Questionnaire (LEQ).
abstract: BACKGROUND
  Brain reserve is a property of the central nervous system related to complex mental activity which may mediate the course and clinical expression of brain injury. Since there is no instrument that comprehensively assesses complex mental activity through the lifespan, we developed and tested the Lifetime of Experiences Questionnaire (LEQ) in a prospective study of healthy ageing.
  
  
  METHODS
  The LEQ assesses educational, occupational and cognitive lifestyle activities at different stages through life. Test-retest, item analysis and Item Response Theory (IRT) were used to determine reliability. Dimensionality was evaluated using factor analysis. Validity was established through IRT analysis of test performance, correlation with an extant contemporaneous instrument (Cognitive Activities Scale; CAS) and prediction of global cognitive change over 18 months controlling for age, baseline cognition and hypertension.
  
  
  RESULTS
  In a sample of healthy older individuals (n=79) the LEQ was found to be consistent, coherent and discriminate between individuals with high and low mental activity levels. Factor analysis revealed a dominant factor which loaded heavily on education, occupation and leisure activity. Total LEQ was significantly correlated with the CAS. Furthermore, individuals with higher LEQ scores showed less cognitive decline over 18 months, independent of covariates (r=0.37, p=0.003).
  
  
  CONCLUSIONS
  The LEQ is a reliable and valid instrument for assessing complex lifespan mental activity which is protective against cognitive decline. The LEQ is therefore proposed as a useful tool for estimating brain reserve in older individuals and further development is anticipated.
authors.affiliation: School of Psychiatry, University of New South Wales, The Neuropsychiatric Institute, Prince of Wales Hospital, NSW, Australia. michaelv@unsw.edu.au
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Valenzuela
authors.forename: Perminder
authors.initials: P
authors.lastname: Sachdev
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D005260:Female; D006801:Humans; D008297:Male; D008606:Mental Processes / Q000502:physiology; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011594:Psychometrics; D012016:Reference Values; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires