Polysomnographic and Subjective Sleep Markers of Mild Cognitive Impairment

Study Objectives: Growing evidence suggests that sleep disturbances precede by years the clinical onset of Alzheimer disease (AD). The goal of the current study is to determine whether changes in polysomnographic (PSG) sleep patterns accompany subjective sleep complaints in patients with mild cognitive impairment (MCI). We further examine whether meaningful changes in objective sleep physiology are predicted by self-reported sleep measures in MCI patients, and whether incipient neurodegeneration contributes to exacerbate sleep misperception. Design, Setting, and Participants: Overnight PSG recordings and self-reported sleep measures were obtained from 25 healthy elderly (HE) subjects and 25 patients with MCI at the sleep laboratory. Results: Both PSG and self-reported sleep measures confirmed that sleep is altered in patients with MCI. Whereas subjective sleep responses predicted fragmentation of slow wave sleep (SWS) in HE individuals, this relationship was not evident in MCI patients. Furthermore, patients with MCI showed significant discrepancies in the estimation of sleep onset latency when compared with HE subjects. Conclusions: Sleep is significantly impaired in patients with mild cognitive impairment at both the objective and subjective level, which may be used as a surrogate marker of preclinical Alzheimer disease. Taken together, these findings aid in the development of novel therapeutic strategies devoted to improve sleep in the elderly population at risk of developing Alzheimer disease.