Der Einfluss des Alterns auf Schlafstruktur und den REM-NREM-Zyklus
Zusammenfassung der Projektergebnisse
Sleep undergoes significant changes across the life cycle. Such changes have been studied intensively from young adulthood to old age in cross-sectional studies. However, little is known about the intra-individual pattern of these changes. For this project, we had the unique opportunity to study the sleep of a cohort of subjects again using polysomnography (PSG, study 2), whose sleep had been PSG-recorded extensively 33 – 46 years ago (study 1). Out of the 19 young, healthy volunteers, who participated in study 1, we were able to contact 15 subjects, who are in the age range of 58 – 75 years now. All of them agreed to have their sleep recorded again in the sleep laboratory of the University Clinic Regensburg, Dept. of Psychiatry, for three consecutive nights. After some delay caused by the COVID-19 pandemic, all PSGs were recorded as planned. In three subjects, who could not come to the sleep lab for personal reasons, home PSG was performed. Sleep stages were scored according to the Rechtschaffen and Kales manual, which had been used for study 1, to enable valid comparisons between study 1 and 2. The participants consistently and significantly showed the typical age-related changes in sleep structure with large effect sizes (Cohen’s D 1.0-3.7): Wake and Stage 1 increased, and SWS decreased in all 15 participants, REM decreased in 13/15 participants. Stage 2 did not change significantly in the mean (D = 0.1). To analyse intra-individual stability, the position of a given participant and variable in study 1 (young) vs. study 2 (aged) in relation to the respective group median (above [+] or below [-] median) was determined. Participant with more congruent pairs (+/+ or -/-, n =8) were younger (62.4 vs. 70.1 years) and had a significantly shorter time span between the two studies (37.8 vs. 45.5 years, p < .001). Due to the delay in performing the sleep recordings, caused by the COVID-19 pandemic, statistical analysis of the data is not yet finished. Presently we are exploring the data set in detail for stage transitions and holding times, the NREM-REM cycle, and eye movement density in REM sleep. The typical age-related changes in sleep architecture known from cross-sectional studies, were confirmed on an intra-individual base. It turned out that those participants with more pronounced sleep alterations had a larger interval between the two measurements times than those with less sleep alterations. This suggests that the rate of change in sleep structure increases continuously with age. This study contributes to the understanding of the effects of aging on sleep. Due to its longitudinal design, with a very long interval between two assessments (33-46 years) in the same cohort, it allows for the first time to estimate the rate of change with aging for each of the different sleep variables. This approach fosters knowledge of the interdependence of aging and sleep and promotes personalised sleep medicine and treatment. More fine-graded longitudinal sleep studies, with repeat studies in the same sample of individuals would allow to assess the interaction of social and biomedical data as well as critical life events with sleep.
