THE DETERMINATION OF CLINICALLY MEANINGFUL COGNITIVE DECLINE - DEVELOPMENT AND USE OF AN ALTERNATIVE METHOD

Statistical methods traditionally used in the analysis of change (e.g. , repeated measures ANOVA) may be inadequate for the investigation of cognitive decline if a study's effect size is small, the variance with in groups is heterogeneous, or the statistical power is law. To examin e an alternative approach to the determination of clinically meaningfu l cognitive decline and investigate whether such decline occurs during the first year after stroke, we administered a neuropsychological tes t battery to 172 patients (age = 70.3 +/- 7.6 years; education = 10.3 +/- 4.7 years) 3 and 12 months after stroke and 199 nondemented stroke -free control subjects (age = 71.1 +/- 6.4 years; education = 12.8 +/- 4.2 years) on two occasions : 12 months apart. Two neuropsychologists classified each subject's test performance as having declined, improv ed, or remained stable based solely on clinical judgment. Reliability of the rating of decline versus the pooled rating of improvement/stabi lity was excellent (kappa = 0.79). The two raring groups differed sign ificantly and in the appropriate directions in change on most rests. W hile a MANOVA comparing the stroke and control groups on change in res t scores was not significant, logistic regression analysis determined that a raring of clinically meaningful cognitive decline was associate d with stroke status (Odds Ratio = 1.8, 95% Confidence Interval = 1.0 to 3.2), while adjusting for demographic factors. We propose that this alternative approach to the analysis of cognitive change can facilita te the recognition of decline in subgroups of subjects. It would be va luable as an adjunct to studies of the incidence of dementia, for exam ple, in which the recognition of cognitive decline might be difficult in highly educated patients whose baseline level of performance is far above the cutoffs operationalized for the diagnosis of dementia.