Impact of sleep characteristics on cognitive performance in Mild Cognitive Impairment (MCI)

Abstract

Introduction and objectives: Cross-sectional studies generally associate poorer sleep quality with lower level of neuropsychological functioning in healthy ageing subjects. However, the relationship between sleep quality and cognitive performance in MCI patients, has not been fully established. The aim of this study was to determine the impact of sleep characteristics on performance in neuropsychological tests, in a sample of patients with MCI. Material and methods: We recruited consecutive patients with diagnosis of MCI according to Mayo Clinic criteria between January and December 2014. Patients underwent one night polysomnography and a neuropsychological battery, including RAVLT, Digit Symbol (DS), digit span, block design and similarities subtest (WAIS), Trail Making Test AB (TMA -TMB), verbal fluency tests, and Wisconsin Card Sorting Test. Sleep measures were scored from the polygraphic records according to conventional criteria including sleep stage time, REM latency (RL), the arousal index, and sleep efficiency(SE). Pearson correlation analysis, ANOVA and Chi 2 were performed. (p < 0,05). Results: The mean age of 36 subjects was 67,28 ± 8,16 years and 20 were females (55.55%). SE positively correlated with MMSE´s score (r = 0.36), DS (r = 0.38), block design (r = 0.41) and inversely correlated with TMTA (r = −0.39), number of false recognition responses (r = −0.37) and sum of intrusions(r = −0.41) in RAVLT. RL is inversely correlated with TMTA(r = −0.36). The other sleep variables showed non correlations with results of cognitive tests. Conclusion: In our sample, MCI patients with lower sleep efficiency showed worse perfomance in visuospatial skills, executive functions and orbitofrontal functioning, while a longer RL correlated with better performance in attention.