Sleep Measures Expressing ‘Functional Uncertainty' in Elderlies' Sleep

Abstract

Background: The notion of ‘functional uncertainty' during sleep was first proposed to indicate an inability of the central nervous system to maintain stable states by coordinating physiological processes. While the presence of functional uncertainty phenomena has been shown in infants and hypothesized in the elderly, its actual occurrence in the aged population has never been systematically investigated. Objective: The aim of the study is to identify, in the sleep of aged individuals, indexes of sleep instability and fragmentation as markers of functional uncertainty, by comparing a sample of healthy elderly subjects to one of young adults. Methods: We compared polysomnograhic recordings of 20 healthy elderly subjects (age range 65-85 years) with those of 20 young individuals (age range 22-32 years), with special regard to the variables expressing functional uncertainty in sleep, such as continuity (e.g. arousals, awakenings), stability (e.g. state transitions, periods of marked ‘functional uncertainty') and cyclic organization parameters. Results: Significant differences emerged for all variables of interest: the elderly group showed higher indexes of fragmentation and instability than the young, as well as less and shorter cycles, and a lower percentage of time spent in cycles. Conclusion: Our results support the hypothesis of a progressive sleep quality disruption with aging, expressed by pronounced sleep instability, fragmentation and disorganization. We propose that functional uncertainty measures could usefully be included in standard sleep assessments on both aged and sleep-disordered populations as accurate sleep quality indexes.

Age affects sleep microstructure more than sleep macrostructure

“…Moreover, more stage shifts and awakenings occurred in older age, which is in concordance with the observation of ‘functional uncertainty’ by Conte et al . (), although the number of arousals was not affected by age, which is in disagreement with previous reports (Conte et al ., ; Dijk et al ., ). This heterogeneity might be due to different criteria used to define arousals, as for example Conte et al .…”

“…This heterogeneity might be due to different criteria used to define arousals, as for example Conte et al . () defined arousals as changes to lighter sleep stages, while in the present study arousals were defined according to the AASM criteria. In addition, the present study did not analyse cyclic alternating patterns, which could cover additional characteristics of sleep instability (Parrino et al ., ).…”

“…Moreover, more stage shifts and awakenings occurred in older age, which is in concordance with the observation of 'functional uncertainty' by Conte et al (2014), although the number of arousals was not affected by age, which is in disagreement with previous reports (Conte et al, 2014;Dijk et al, 2001). This heterogeneity might be due to different criteria used to define arousals, as for example Conte et al (2014) defined arousals as changes to lighter sleep stages, while in the present study arousals were defined according to the AASM criteria. In addition, the present study did not analyse cyclic alternating patterns, which could cover additional characteristics of sleep instability (Parrino et al, 2012).…”

Sleep and Human Aging

“…Advancing into the fifth decade of older age and beyond are a collection of well-characterized changes in sleep architecture (Figure 1A): (1) advanced sleep timing (i.e., earlier bedtimes and rise times), (2) longer sleep-onset latency (i.e., longer time taken to fall asleep), (3) shorter overall sleep duration, (4) increased sleep fragmentation (i.e., less consolidated sleep with more awakenings, arousals, or transitions to lighter sleep stages), (5) more fragile sleep (i.e., higher likelihood of being woken by external sensory stimuli), (6) reduced amount of deeper NREM sleep known as slow wave sleep (SWS), (7) increased time spent in lighter NREM stages 1 and 2, (8) shorter and fewer NREM-REM sleep cycles, and (9) increased time spent awake throughout the night (Conte et al, 2014; Feinberg and Carlson, 1968; Kales et al, 1967; Klerman and Dijk, 2008; Landolt et al, 1996; Ohayon et al, 2004; Redline et al, 2004; Van Cauter et al, 2000; Vienne et al, 2016; Webb and Campbell, 1979; Zepelin et al, 1984). This is not to suggest a lack of individual variability in the degree of sleep disruption.…”

Is Sleep Disruption a Cause or Consequence of Alzheimer’s Disease? Reviewing Its Possible Role as a Biomarker

“…Regarding sleep stages, NREM-REM sleep cycles were fewer and shorter. Aging was characterized by a linear decrease in the proportion of REM [60,61] and a reduced amount of deep NREM sleep, compensated with an increased duration of light NREM [47,[64][65][66]. These changes in sleep architecture during adulthood have been confirmed by two different meta-analyses, one of which included subjects from childhood to old age [61,62].…”