A sleep continuity scale in Alzheimer’s disease: validation and relationship with cognitive and functional deterioration

Abstract

Considering that disrupted sleep may be detrimental to daytime performance in people with dementia, we set out to construct a questionnaire able to identify sleep patterns potentially associated with clinical and functional disease variables in this population. Two subsets of items indicative of patterns of unstable sleep and of disordered rapid eye movement sleep (REM) were selected. The first included items investigating sleep continuity, with low sleep continuity markers considered indicative of high arousability; the second included items investigating the frequency and quality of dreams and the frequency of clinically identifiable REM sleep behaviour disorder episodes. The questionnaire was administered to 140 outpatients with a diagnosis of mild-to-moderate Alzheimer's disease. The Mini-Mental State Examination (MMSE), Activities of Daily Living (ADL), Instrumental Activities of Daily Living, Neuropsychiatric Inventory and Clinical Dementia Rating (CDR) were administered to quantify cognitive, functional and behavioural impairment. A subscale comprising items investigating sleep discontinuity/fragmentation and showing high internal consistency was constructed and found to correlate significantly with variables considered indexes of cognitive and functional deterioration in AD (MMSE, ADL and CDR). Conversely, it did not prove possible to obtain a subscale of dysfunctional REM phenomena. The use of a rapidly and easily administered sleep scale, like the one we constructed, appears to be suitable for early identification and longitudinal monitoring of sleep disturbances in AD.