The characterisation and impact of 'fluctuating' cognition in dementia with Lewy bodies and Alzheimer's disease

Background Case reports and clinical observations suggest that fluctuating cognition (FC) is common in all the major dementias, particularly dementia with Lewy bodies (DLB) where it is one of three core clinical diagnostic features. The purpose of this study was to characterise FC and determine its impact upon activities of daily living. Methods Forty matched subjects (15 DLB, 15 AD, 10 elderly controls) were assessed using the activities of daily living scale (ADLD), the cognitive drug research (CDR) computerised neuropsychological test battery and a semi-standardised assessment of FC. The CDR battery was completed three times across: a 1-week period, to evaluate variability in attention, visuospatial ability, working memory and delayed recall. Results There was a strong positive correlation between clinical FC scores and total mean ADLD. Measures of cognitive variability also demonstrated strong significant correlations with independent clinical severity ratings of FC across several cognitive domains. These associations were most powerful between attentional measures and clinical FC ratings. Conclusions Although attention is the cognitive domain which fluctuates most markedly, other cognitive domains are also affected. FC also has a significant independent impact on activities of daily living. Copyright (C) 2001 John Wiley & Sons, Ltd.