Subclinical epileptiform activity during sleep in Alzheimer's disease and mild cognitive impairment

Objective: Recent findings suggested that subclinical epileptiform activity is prevalent during sleep in a significant proportion of Alzheimer's Disease (AD) patients.

The aims of our study were: (A) comparing the frequency of subclinical epileptiform activity during the sleep in a sample diagnosed with 'probable' AD and Mild Cognitive Impairment (MCI) due to AD, and in healthy subjects; (B) evaluating epileptiform EEG activity as a function of different sleep stages within a well-controlled polysomnographic setting.

Methods: We prospectively enrolled 50 'probable' AD patients (73 ± 7.0 years) and 50 subjects with MCI due to AD (72 ± 6.7 years) without history of seizures, comparing them with 50 controls (69 ± 6.7 years). Patients underwent to a full-night video-PSG.

Results: Subclinical epileptiform activity was detected in 6.38% of 'probable' AD patients, 11.63% of MCI due to AD subjects and 4.54% of controls (p = 0.43). The comparisons between the three groups for the frequency of epileptiform activity did not reach statistically significant differences neither for total sleep nor for any sleep period considered.

Conclusions: Our study shows that, when controlling for sleep stages and the influence of psychoactive drugs, AD patients and MCI due to AD subjects do not exhibit a higher frequency of epileptiform discharges during sleep compared to healthy subjects.

Significance: Subclinical epileptiform activity during sleep does not discriminate 'probable' AD from MCI due to AD and healthy controls.