Dementia with Lewy Bodies. Identification, frequency and sleep-disturbances. A cross-sectional clinical dementia cohort study

Background: Dementia with Lewy Bodies (DLB) has existed as a formal consensus diagnosis since 1996 and is defined by dementia and the core features parkinsonism, visual hallucinations and cognitive fluctuations. The original consensus criteria had low sensitivity (20-60%) although the specificity was satisfying. (80-100%) From 2005 the additional suggestive features rapid eye movement (REM) sleep behaviour disorder (RBD), low uptake on Dopamine Transporter Scan (DaTSCAN ) and neuroleptic sensitivity have been included to improve sensitivity of the clinical diagnosis. The nosological status of DLB is still discussed, and the frequencies of DLB, and of RBD and other sleep disturbances in DLB, are not known. Objectives: In our first paper we sought to find the frequency of DLB in the Dementia Study of Western Norway, (The DemVest-Study) applying the revised clinical diagnostic DLBcriteria. We compared the frequency of DLB in our cohort applying both the new revised and the original consensus criteria for diagnosing DLB to find if the new criteria are more sensitive. In the second paper we compared the frequency of sleep disturbances in Lewy Body Dementia (LBD) as compared to Alzheimer’s Dementia (AD) and healthy controls. In the third paper we examined how the core and suggestive features of DLB were distributed among all individuals with mild dementia to find empirical support for diagnosing DLB as an own diagnostic entity and to find cut- off values for core and suggestive features designating DLB. Methods: All referrals to 5 specialists out patient clinics doing dementia work up in Western Norway were screened during a 2 year inclusion period. Particular care was taken to screen all included patients for the core and suggestive features of DLB. We offered inclusion to everybody presenting with a first time diagnosis of mild dementia with a MMSE score 20. Exclusion criteria were normal cognition or mild cognitive impairment, severe dementia, organic or functional psychosis and a diagnosis of severe or terminal physical illness. For the first paper dementia was diagnosed according to DSM-IV criteria and DLB according to both the 1996 and 2005 criteria. For the second paper we applied the Mayo Sleep Questionnaire (MSQ) and the Neuropsychiatric Inventory (NPI) to screen for sleep disturbances. Healthy elderly subjects from the Mayo Clinic Study of Aging were available for comparison. In the third paper we used a two step cluster analysis to classify persons with mild dementia according to continuous scores on scales for the DLB symptoms; hallucinations, fluctuations, parkinsonism and RBD. Results: 196 subjects were included in the first paper and of these 20 % had DLB according to the revised consensus criteria. We compared the 1996 criteria to the 2005 criteria and found a 25% increase in patients fulfilling the probable DLB category with the new criteria. The proportion with DLB did not differ according to age bands and dementia severity. (CDR) In the second paper 155 patients with mild dementia who had a caregiver who was also their bed-partner and 420 age matched controls without dementia were included. Participants with Lewy Body Dementia, i.e. DLB and PDD combined, had significantly more sleep disturbances than those with AD (89% vs. 64%, p=0.008) particularly regarding RBD. (39% vs. 9%, p