Fluctuations in Cognition and Alertness Vary Independently in Dementia With Lewy Bodies

• Type of Material: Article
• Authors: Donald Bliwise, Emory University; Michael K. Scullin, Emory University; Lynn Trotti, Emory University
• Language: English
• Date: 2014-01-01
• Publisher: Wiley
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2013 Movement Disorder Society.
• Final Published Version (URL): http://dx.doi.org/10.1002/mds.25707
• Title of Journal or Parent Work: Movement Disorders
• ISSN: 0885-3185
• Volume: 29
• Issue: 1
• Start Page: 83
• End Page: 89
• Grant/Funding Information: M.K.S. was partially supported by an Emory University Cottrell Fellowship.; This work was supported by the United States National Institutes of Health (grant number R01 NS-050595 to D.L.B., F32 AG-041543 to M.K.S., KL2 RR-025009 to L.M.T., UL1 RR-025008 for the Atlanta Clinical and Translational Science Institute).
• Keywords: DAYTIME SLEEPINESS; Science & Technology; digit span; ALZHEIMERS-DISEASE; WAKEFULNESS TEST; DLB; cognition; PARKINSONS-DISEASE; Clinical Neurology; ATTENTION; Neurosciences & Neurology; DIAGNOSIS; DISORDERS; fluctuations; MAINTENANCE; alertness; CLINICIAN; dementia with Lewy bodies; Life Sciences & Biomedicine
• Research Categories: Biology, Neuroscience

Abstract

Fluctuations in mental status are 1 of the core diagnostic criteria for dementia with Lewy bodies (DLB) and are thought to reflect variability in daytime alertness. Previous attempts to study fluctuations have been limited to caregiver reports, observer rating scales, short segments of electroencephalography, or motor-dependent, reaction time tests. Concordance among such measures is often poor, and fluctuations remain difficult to quantify. We compared fluctuations in cognition and alertness in patients with DLB (n=13) and idiopathic Parkinson's disease (PD) (n=64), a condition associated with deficits in daytime alertness. We systematically and repeatedly collected cognitive and physiologic measures during a 48-hour inpatient protocol in a sound-attenuated sleep laboratory in a geriatric hospital. Cognitive fluctuations were analyzed using coefficients of variation (COVs) derived from performance on a bedside examination familiar to clinicians (digit span). Alertness fluctuations were assessed objectively using COVs from the polysomnographically-based Maintenance of Wakefulness Test. Despite predictably lower mean digit span performances, DLB patients demonstrated significantly greater cognitive fluctuations than PD patients (P<0.001), even when groups were matched on general cognitive impairment. There were no group differences in alertness fluctuations, although DLB patients were less alert than PD patients not receiving dopaminergics. The prevailing assumption that fluctuations in cognition in DLB are reflected in fluctuations in daytime alertness was not supported by objective, physiological measurements. Fluctuating mental status in DLB patients can be detected with repeated administration of a simple bedside exam that can be adapted to a clinic setting.