Daytime sleepiness in mild Alzheimer's disease with and without parkinsonian features

Excessive daytime sleepiness (EDS) and nocturnal sleep disruption are common in Alzheimer's disease (AD). However, little is known regarding risk factors for developing EDS and sleep disruption in AD. In AD, EDS is associated with parkinsonian motor features (PF), which are associated with faster cognitive decline. The primary aim of this exploratory study was to evaluate whether differences in EDS and nocturnal sleep disruption exist between AD participants with versus without PF.

Thirty-six participants with mild AD were evaluated for PF using the modified motor UPDRS (mmUPDRS) scoring system and classified according to absence (AD-PF, n=19) or presence (AD+PF, n=17) of PF. EDS was assessed using questionnaires and a multiple sleep latency test (MSLT) performed the day after nocturnal polysomnogram. Participants were considered "Sleepy" or "Not Sleepy" according to mean MSLT scores (cutoff score=10.4 min).

Results showed that the AD+PF group were sleepier than the AD-PF group by subjective and objective measures, despite similarities in nocturnal sleep. The AD+PF group had higher scores on the Epworth Sleepiness Scale (8.5 versus 3.9, p=.001). The AD+PF group also had higher percentage of participants that had "Sleepy" MSLT scores compared to the AD-PF group (75% versus 31.6%, respectively; χ(2)=6.56, p=.01).

The presence of parkinsonian features may be an independent risk factor for sleepiness in mild AD.