Item analysis of ADAS-Cog: effect of baseline cognitive impairment in a clinical AD trial.
We explored the association of Alzheimer's disease (AD) Assessment Scale (ADAS-Cog) item scores with AD severity using cross-sectional and longitudinal data from the same study. Post hoc analyses were performed using placebo data from a 12-month trial of patients with mild-to-moderate AD (N =281 randomized, N =209 completed). Baseline distributions of ADAS-Cog item scores by Mini-Mental State Examination (MMSE) score and Clinical Dementia Rating (CDR) sum of boxes score (measures of dementia severity) were estimated using local and nonparametric regressions. Mixed-effect models were used to characterize ADAS-Cog item score changes over time by dementia severity (MMSE: mild =21-26, moderate =14-20; global CDR: mild =0.5-1, moderate =2). In the cross-sectional analysis of baseline ADAS-Cog item scores, orientation was the most sensitive item to differentiate patients across levels of cognitive impairment. Several items showed a ceiling effect, particularly in milder AD. In the longitudinal analysis of change scores over 12 months, orientation was the only item with noticeable decline (8%-10%) in mild AD. Most items showed modest declines (5%-20%) in moderate AD.
Sevigny
Jeffrey J
JJ
Merck Research Laboratories, North Wales, PA, USA. jeffrey.sevigny@novartis.com
Peng
Yahong
Y
Liu
Lian
L
Lines
Christopher R
CR
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000175:diagnosis / Q000523:psychology*; D003071:Cognition; D003072:Cognition Disorders / Q000175:diagnosis / Q000523:psychology*; D003430:Cross-Sectional Studies; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008609:Mental Status Schedule; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D012044:Regression Analysis; D012720:Severity of Illness Index