title: Evaluation and correction for a 'training effect' in the cognitive assessment of older adults.
abstract: BACKGROUND
  Repeated administration of psychometric instruments frequently results in a higher score on retesting, the so-called training effect. Yet, a training effect has been poorly considered in longitudinal studies of cognitive changes in older persons.
  
  
  METHODS
  We investigated the presence, magnitude and potential adjustments for training effect in the older participants of the Systolic Hypertension in the Elderly Program (SHEP). SHEP evaluated the cognitive status effects of a diuretic-based treatment of isolated systolic hypertension versus placebo. Changes in the short Comprehensive Assessment and Referral Evaluation (short-CARE) questionnaire score, from baseline through 4 years of follow-up, were assessed in 4,718 participants. In this study, we used two regression techniques to adjust data for the training effect.
  
  
  RESULTS
  In both study groups, a training effect was evident as a progressive improvement in the short-CARE score throughout year 1. Thereafter, cognitive scores tended to deteriorate, more in the placebo than in the active treatment group (p = 0.055). When follow-up scores were adjusted based upon baseline data, the difference between the study groups reached statistical significance (p = 0.019), but the apparent overall trend towards deterioration in cognitive score was no longer observed. Adjustment of baseline data preserved this apparent temporal course, but did not improve the discrimination between the two study groups (p = 0.165).
  
  
  CONCLUSIONS
  In SHEP, repeated cognitive assessments were likely biased by a training effect which could be only partially corrected by statistical techniques. Studies of changes in the cognitive status of older persons should be designed appropriately to estimate and minimize the consequences of a training effect in follow-up data.
authors.affiliation: Sticht Center on Aging, Wake Forest University Baptist Medical Center, Winston-Salem, NC 27157, USA. mdibari@wfubmc.edu
authors.forename: M
authors.initials: M
authors.lastname: Di Bari
authors.forename: M
authors.initials: M
authors.lastname: Pahor
authors.forename: M
authors.initials: M
authors.lastname: Barnard
authors.forename: N
authors.initials: N
authors.lastname: Gades
authors.forename: M
authors.initials: M
authors.lastname: Graney
authors.forename: L V
authors.initials: LV
authors.lastname: Franse
authors.forename: B W J H
authors.initials: BW
authors.lastname: Penninx
authors.forename: N
authors.initials: N
authors.lastname: Marchionni
authors.forename: W B
authors.initials: WB
authors.lastname: Applegate
mesh_terms: D000368:Aged; D015982:Bias; D003072:Cognition Disorders / Q000175:diagnosis*; D005260:Female; D015577:Geriatric Assessment; D006801:Humans; D007858:Learning; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011594:Psychometrics; D016032:Randomized Controlled Trials as Topic; D012044:Regression Analysis; D015203:Reproducibility of Results; D012107:Research Design; D013647:Task Performance and Analysis