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Sleep Breath. 2019 Nov 30. doi: 10.1007/s11325-019-01970-9. [Epub ahead of print]

Sleep spindles, K-complexes, limb movements and sleep stage proportions may be biomarkers for amnestic mild cognitive impairment and Alzheimer's disease.

Liu S1, Pan J2, Tang K1, Lei Q1, He L1, Meng Y1, Cai X1, Li Z3,4,5.

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Department of Neurology, The Sixth Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510655, China.
Department of Psychology, Sun Yat-sen University, Guangzhou, 510006, China.
Department of Neurology, The Sixth Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510655, China.
Shenzhen Research Institute, Sun Yat-Sen University, Shenzhen, China.
Guangdong Provincial Key Laboratory of Brain Function and Disease, Guangzhou, 510080, China.



Sleep disturbances are common in Alzheimer's disease (AD) and mild cognitive impairment (MCI) patients. Non-rapid eye movement stage 3 (N3), rapid eye movement stage (REM), spindle density, and K-complex (KC) density are decreased in MCI and AD patients. Periodic limb movements in sleep (PLMS) are increased in other neurodegenerative diseases. We aimed to distinguish amnestic mild cognitive impairment (aMCI) patients from the overall population of MCI patients by comparing the N3 and REM proportions, the morphological characteristics of spindles and KCs and the periodic limb movement index (PLMI) among control, aMCI and AD subjects.


In 92 subjects (30 controls, 32 aMCI and 30 AD), sleep stages, spindles, KCs and PLMS were recorded during the second of two nights of polysomnography (PSG). We compared the above parameters among the three groups.


AD and aMCI subjects had lower proportions of N3 and REM, poorer spindle and KC activities and more frequent PLMS than controls. These alterations were associated with decreased Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores. We determined cut-off values for distinguishing aMCI and AD using logistic regression and receiver operating characteristic (ROC) analyses.


AD and aMCI patients have abnormal sleep stage proportions, spindles, KCs and PLMS. The combination of the above alterations may distinguish aMCI and AD patients from controls with high specificity and sensitivity.


Alzheimer’s disease; Amnestic mild cognitive impairment; K-complex; Periodic limb movements; Polysomnography; Sleep spindle; Sleep stages


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