Association of β-Amyloid Burden With Sleep Dysfunction and Cognitive Impairment in Elderly Individuals With Cognitive Disorders

IMPORTANCE: Evidence shows that sleep dysfunction and β-amyloid (Aβ) deposition work synergistically to impair brain function in individuals with normal cognition, increasing the risk of developing dementia later in life. However, whether Aβ continues to play an integral role in sleep dysfunction after the onset of cognitive decline in individuals with dementia is unclear. OBJECTIVE: To determine whether Aβ deposition in the brain is associated with subjective measures of sleep quality and cognition in elderly individuals with cognitive disorders. DESIGN, SETTING, AND PARTICIPANTS: A nested survey study was conducted at the Cognitive Disorders and Comprehensive Alzheimer Disease Center of Thomas Jefferson University Hospital in Philadelphia, Pennsylvania. Participants included patients aged 65 years and older with cognitive disorders verified by neuropsychological testing. Eligible participants were identified from a referral center–based sample of patients who underwent fluorine 18–labeled florbetaben positron emission tomography imaging at Thomas Jefferson University Hospital as part of the multicenter Imaging Dementia-Evidence for Amyloid Scanning study. Data collection and analysis occurred between November 2018 and March 2019. MAIN OUTCOMES AND MEASURES: Sleep quality was measured via responses to sleep questionnaires, Aβ deposition was measured via fluorine 18–labeled florbetaben positron emission tomography, and cognition was measured via Mini-Mental State Examination (MMSE) performance. RESULTS: Of the 67 eligible participants, 52 (77.6%) gave informed consent to participate in the study. Of the 52 enrolled participants (mean [SD] age, 76.6 [7.4] years), 27 (51.9%) were women. Daytime sleepiness was associated with Aβ deposition in the brainstem (B = 0.0063; 95% CI, 0.001 to 0.012; P = .02), but not MMSE performance (B = −0.01; 95% CI, −0.39 to 0.37; P = .96). The number of nocturnal awakenings was associated with Aβ deposition in the precuneus (B = 0.11; 95% CI, 0.06 to 0.17; P < .001) and poor MMSE performance (B = −2.13; 95% CI, −3.13 to −1.13; P < .001). Mediation analysis demonstrated an indirect association between Aβ deposition and poor MMSE performance that relied on nocturnal awakenings as an intermediary (B = −3.99; 95% CI, −7.88 to −0.83; P = .01). CONCLUSIONS AND RELEVANCE: Nighttime sleep disruption may mediate the association between Aβ and cognitive impairment, suggesting that there is an underlying sleep-dependent mechanism that links Aβ burden in the brain to cognitive decline. Further elucidation of this mechanism may improve understanding of disease processes associated with Aβ accumulation.