Background: Dementia with Lewy bodies (DLB) is the second most common type of neurodegenerative dementia. It is frequently difficult to differentiate DLB from Alzheimer's disease (AD) and other types of dementia. This study examined the usefulness of monitoring sleep talking for the diagnosis of DLB.

Methods: A total of 317 patients with dementia were selected from a consecutive series at the Dementia Clinic of Kumamoto University Hospital. Diagnostic categories consisted of probable DLB (n = 55), probable AD (n = 191), frontotemporal lobar degeneration (FTLD) (n = 16), vascular dementia (VaD) (n = 18), and other/unspecified dementia (n = 37). We evaluated sleep talking in all dementia patients and normal elderly subjects (n = 32) using an originally designed sleep talking questionnaire.

Results: Sleep talking occurred most frequently in the DLB group (61.8%), followed by the VaD group (33.3%), other/unspecified dementia group (27.0%), AD group (18.8%), FTLD group (12.5%), and normal elderly subjects group (6.3%). The prevalence of sleep talking in the DLB group was significantly higher than in other groups, except in the VaD group. The sleep talking yielded high specificity (81.2%) and some sensitivity (61.8%) for the differential diagnosis of DLB from AD. Furthermore, loud sleep talking may improve the specificity (96.9%). For the differentiation of DLB from all other dementia types, the specificity of sleep talking and loud sleep talking was also high (79.4% and 95.8% respectively).

Conclusions: Assessing sleep talking, especially the volume of sleep talking, may be useful in the clinical discrimination of DLB from not only AD but also from all other types of dementia.