Non-amnestic mild cognitive impairment and sleep complaints: a bidirectional relationship?

Background: Prior studies documented that several sleep disorders may coexist in patients affected by Mild Cognitive Impairment (MCI) and Alzheimer disease (AD), and have a strong bidirectional relationship with cognitive decline.

Aim: To assess the self-reported sleep quality and daytime sleepiness among subjects affected by MCI and AD at early-stage and healthy controls, and to verify if sleep disturbances might be an indicator of specific cognitive deficits.

Methods: 139 patients (102 MCI, 37 AD) underwent comprehensive neuropsychological, functional, and behavioral assessment, which also included Epworth Sleepiness Scale (ESS) and Pittsburgh Sleep Quality Index (PSQI). 80 healthy elderly subjects were used as controls. MCI patients have been divided into Good Sleepers and Bad Sleepers, depending on their reported sleep quality (PSQI global score ≤5/>5).

Results: MCI patients experienced more subjective daytime sleepiness than AD matches. As for the subjective sleep quality among MCI patients, 54% of Bad Sleepers met diagnostic criteria for non-amnestic MCI; vice-versa, 73% of Good Sleepers were diagnosed with amnestic-MCI (p = 0.005), independently of depression and anxiety.

Conclusions: MCI patients complain of daytime sleepiness and dysfunction more than AD patients; among MCI patients, Bad Sleepers appear mainly characterized by a non-amnestic cognitive profile.