Υπνική συμπεριφορά και επίπτωση ήπιας νοητικής έκπτωσης σε Έλληνες ηλικιωμένους

Abstract

Background: Sleep is crucial for cognition, particularly for memory, given its complex association with neurodegenerative processes. The aim of the present study was to examine the association between sleep quality as well as sleep duration and memory performance in a Greek elderly population.Setting: Cross-sectional design in the Hellenic Longitudinal Investigation of Aging and Diet (HELIAD), a population representative study of Greek elderly (65 years or older).Methods: Data from 1589 participants free of sleep medication were included. Sleep quality was esti- mated by using the Sleep Scale from the Medical Outcomes Study. An extensive neuropsychological assessment examining memory was administered to each participant. Linear regression analyses were used to examine whether sleep quality (higher score, poor quality) and/or sleep duration were associated with memory expressed in the form of a z-score. Age, sex, education, and body mass index were included as covariates. The main analyses were conducted first on the total sample, then with the exclusion of demented participants, and finally with the exclusion of both demented and participants with Mild Cognitive Impairment (MCI). We then conducted further analyses on the non-demented, non-MCI group, initially stratified by Apolipoprotein E-e4 gene. We further examined the role of co-morbidities, as well as the association between sleep duration groups and memory. We also explored any interaction effect between sex and sleep quality/duration on memory. We then examined the associations between com- ponents of sleep measures and memory scores. Lastly, we examined the associations between sleep qual- ity/duration and verbal/non-verbal memory separately.Results: In the total sample, we noted significant associations between sleep duration and memory (B = 0.001, p 0.0001), but not for sleep quality and memory (B = 0.038, p = 0.121). After excluding the demented participants, the associations were significant for: sleep quality and memory (B = 0.054, p = 0.023), and sleep duration and memory (B = 0.001, p 0.0001). After excluding both the MCI and the demented subjects, the associations between sleep quality and memory (B = 0.065, p = 0.006), and sleep duration and memory (B = 0.001, p = 0.003) were still significant. The association between the sleep duration groups and memory function was also significant, such that poor memory performance was associated with the longer sleep duration group. The results remained significant even after controlling for the co-morbidities, as well as after adding in the model anxiety and depression as covariates. Associations between sleep quality and memory, and sleep duration and memory were pre- sent in the ApoE-e4 non-carriers. The individual sleep questions that were probably shown to be drivingthe associations between sleep and memory were: time to fall asleep, sleep not quiet, getting enough sleep to feel rested upon waking in the morning, and getting the amount of sleep needed. Sleep duration was associated with both verbal and non-verbal memory, while sleep quality was only associated with verbal memory.Conclusion: Poor sleep quality and longer sleep duration were linked to low memory performance, inde- pendent of demographic and clinical factors, in a large sample of cognitively healthy older Greek adults. Other parameters than sleep and memory measurements could play an important role on the association. Levels of melatonin, or circadian rhythms dysregulation might play a crucial role in the above associations.

Στην παρούσα μελέτη, ερευνήσαμε τις σχέσεις μεταξύ ποιότητας και διάρκειας ύπνου και μνημονικής επίδοσης, σε ένα μεγάλο δείγμα από ηλικιωμένους Έλληνες. Λαμβάνοντας υπ’ όψιν παράγοντες όπως η ηλικία, το φύλο, η εκπαίδευση και ο ΔΜΣ, βρήκαμε ότι κακή ποιότητα ύπνου συσχετίστηκε με χαμηλή μνημονική επίδοση. Τα αποτελέσματα παρέμειναν σημαντικά αφού προσθέσαμε ως συμμεταβλητές το άγχος, την κατάθλιψη, και τη συννοσηρότητα. Επιπλέον, οι συμμετέχοντες που ανέφεραν μεγαλύτερη διάρκεια ύπνου παρουσίασαν χαμηλή μνημονική επίδοση. Οι παραπάνω συσχετίσεις ήταν σημαντικές για τους μη φορείς του ApoE-ε4 γονιδίου. Οι υπόλοιπες γνωστικές λειτουργίες δεν συσχετίστηκαν με την ποιότητα ή την διάρκεια ύπνου. Οι πιο σημαντικές ερωτήσεις προβλημάτων ύπνου που συσχετίστηκαν με την μνήμη ήταν: χρόνος που χρειάζεται μέχρι να αποκοιμηθείς, αίσθημα ότι ο ύπνος ήταν ανήσυχος, να μην κοιμάσαι αρκετά (ώστε να νιώθεις ξεκούραστος). Τα δύο φύλα φάνηκε να μην έχουν στατιστικά σημαντική διαφορά στις συσχετίσεις μεταξύ ποιότητας/ διάρκειας ύπνου και μνημονικής επίδοσης.