Drowsiness and daytime sleepiness (despite getting adequate sleep the night before) are often described by individuals with dementia with Lewy bodies (DLB) and their caregivers. This is reported even in the very early (mild cognitive impairment) stage of DLB. Experts have wondered whether sleepiness is a unique feature of DLB, or if it is a part of fluctuating cognition. New research using formal sleep studies reveals that daytime sleepiness not due to poor sleep the night before, can occur in the absence of cognitive fluctuations, and is more likely to occur in DLB than Alzheimer’s disease (AD).
Researchers at Mayo Clinic, led by Tanis Ferman, PhD, studied 61 patients with DLB and 26 with AD. Patients also had a reliable informant complete a subjective questionnaire on sleepiness. All participants had an overnight polysomnography performed to detect sleep efficiency (the proportion of time spent in bed actually asleep) and underlying sleep disorders such as sleep apnea. A subgroup of 32 DLB and 18 AD patients were then assessed to determine how long it took them to fall asleep during four daytime naps. Autopsies were performed (an average of four years later) on 20 of the individuals with DLB, confirming the clinical diagnosis was correct. None of those with AD underwent autopsy.
In the four daytime nap opportunities, over 80% of the DLB group fell asleep within 10 minutes, compared to just under 40% of the AD group. Furthermore, pathologic sleepiness, which was defined by falling asleep in less than 5 minutes, occurred in nearly 60% of the DLB compared to less than 20% of the AD group. In Alzheimer’s, those with greater daytime sleepiness were at a more advanced stage of their dementia. In contrast, patients with dementia with Lewy bodies had an increased chance of falling asleep during the day regardless of dementia severity. In addition, DLB daytime sleepiness was not related to poor sleep quality the night before, and was not associated with parkinsonism or its treatment.
Excessive sleepiness (based on both informant reports and the formal nap evidence) was not related to the presence of visual hallucinations, parkinsonism or REM sleep behavior disorder. While sleepiness in DLB may contribute to fluctuating cognition, this study confirmed that sleepiness often occurs in patients who do not have fluctuating cognition. Daytime sleepiness may be attributed to neuronal changes in the brain sleep-wake systems in patients with DLB.
This research suggests that daytime sleepiness is a distinct symptom of DLB that is independent of disease stage or the presence of the primary symptoms of DLB, and can be distinguished from AD. More research is required to determine whether daytime sleepiness will help improve diagnosis.
Several members of the Lewy Body Dementia Association’s Scientific Advisory Council are authors of this study: Tanis Ferman, PhD, and Dennis Dickson, MD, of Mayo Clinic, Jacksonville, FL, and Bradley Boeve, MD of Mayo Clinic, Rochester, MN.
Funding for this study was provided by the National Institutes of Health and the Mangurian Foundation for Lewy Body Dementia Research.