It is now clear that the relationship between Alzheimer's disease and sleep characteristics go well beyond the widespread finding of sleep disorders in these patients, both because sleep alterations seem to be a risk factor for the disease and because good sleep plays a central role in the elimination of "bad" metabolites of b-amyloid protein, facilitating the aggregation and deposition typical of Alzheimer’s. 

However, the scientific literature lacked a description of the electroencephalographic (EEG) alterations of sleep in these patients and their relationship with the already described alterations of the EEG during the waking state. In almost 10 years of work, a group of researchers from Sapienza University and IRCCS San Raffaele Rome, in collaboration with IRCCS Fondazione Policlinico Universitario Gemelli and the University of L'Aquila, has carried out a study to fill this gap. The result is an extensive study and the first ever in the world in which regional and frequency EEG activities were compared to waking EEG activities recorded at different times throughout the day (to check for the influence of circadian factors). The results of this extensive project have just been published in Science's Open Access journal (IScience).

"It all started about ten years ago - says Luigi De Gennaro and Paolo M. Rossini, research coordinators - when we set ourselves the goal of jointly studying the specific daytime and night-time alterations of brain electrical activity in a large group of patients with Alzheimer's disease. The basic idea was to verify if there were specific alterations in the sleep of these patients and if these presented a relationship with those already known during wakefulness. The main findings of the study were: (1) in both clinical groups (Alzheimer's and MCI, or Mild Cognitive Impairment, an intermediate stage between dementia and normal ageing) a slowing of brain rhythms in REM sleep comparable to that already described in wakefulness; (2) this REM sleep phenomenon correlates with cognitive decline in patients; (3) a drastic decrease in the sigma activity of NREM sleep, again in both clinical groups; (4) a consistent reduction in the function of sleep in allowing brain recovery processes consequent to wakefulness activities."

The implications of this study may open new horizons for specific treatments of sleep alterations in general in the elderly and specifically in Alzheimer's disease and, even more, for the specific MCI picture that in many cases is the antechamber of Alzheimer's.

References:

EEG aterations during wake and sleep in mild cognitive impairment and Alzheimer's disease - Aurora D'Atri, Serena Scarpelli, Maurizio Gorgoni, Camillo Marra, Paolo Maria Rossini, Luigi De Gennaro - IScience 2021. DOI https://doi.org/10.1016/j.isci.2021.102386

Further Information

Luigi De Gennaro 
Department of Psychology
luigi.degennaro@uniroma1.it