Sleep symptoms in syndromes of frontotemporal dementia and Alzheimer's disease: A proof-of-principle behavioural study

Abstract

Sleep disruption is a key clinical issue in the dementias but the sleep phenotypes of these diseases remain poorly characterised. Here we addressed this issue in a proof-of-principle study of 67 patients representing major syndromes of frontotemporal dementia (FTD) and Alzheimer's disease (AD), in relation to 25 healthy older individuals. We collected reports on clinically-relevant sleep characteristics - time spent overnight in bed, sleep quality, excessive daytime somnolence and disruptive sleep events. Difficulty falling or staying asleep at night and excessive daytime somnolence were significantly more frequently reported for patients with both FTD and AD than healthy controls. On average, patients with FTD and AD retired earlier and patients with AD spent significantly longer in bed overnight than did healthy controls. Excessive daytime somnolence was significantly more frequent in the FTD group than the AD group; AD syndromic subgroups showed similar sleep symptom profiles while FTD subgroups showed more variable profiles. Sleep disturbance is a significant clinical issue in major FTD and AD variant syndromes and may be even more salient in FTD than AD. These preliminary findings warrant further systematic investigation with electrophysiological and neuroanatomical correlation in major proteinopathies.

Keywords: Alzheimer’s disease; Frontotemporal dementia; Progressive aphasia; Semantic dementia; Sleep.

Fig. 1

Usual daily rest periods for individual participants. Estimated usual times of retiring and rising each day (24 h clock time on the y-axis) and intervening periods of time in bed have been plotted for all individuals in each of the participant groups: healthy older controls, patients with behavioural variant frontotemporal dementia (bvFTD), semantic dementia (SD), progressive nonfluent aphasia (PNFA), typical amnestic Alzheimer’s disease (tAD) and posterior cortical atrophy (PCA). Individual plots have been ordered within groups according to estimated usual time of retiring. Average times of retiring (horizontal dashed line) and rising (horizontal dotted line) are indicated for each group.