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.

S and full research articles published in SLEEP, the official journal of the APSS. Sleep and sleep disorder scientific findings.

Summary: Studies on sleep during the Covid‐19 pandemic have mostly been conducted during the first wave of contagion (spring 2020). To follow up on two Italian studies addressing subjective sleep features during the second wave (autumn 2020), here we assess sleep during the third wave (spring 2021) in a sample of healthy adults from Campania (Southern Italy). Actigraphic data (on 2 nights) and the Pittsburgh Sleep Quality Index were collected from 82 participants (40 F, mean age: 32.5 ± 11.5 years) from 11 March to 18 April 2021, when Campania was classified as a “red zone”, i.e. it was subjected to strict restrictions, only slightly looser than those characterizing the first national lockdown (spring 2020). Although objective sleep duration and architecture appeared in the normal range, the presence of disrupted sleep was indexed by a relevant degree of sleep fragmentation (number of awakenings ≥ 1 min: 12.7 ± 6.12; number of awakenings ≥ 5 min: 3.04 ± 1.52), paralleled by poor subjective sleep quality (Pittsburgh Sleep Quality Index global score: 5.77 ± 2.58). These data suggest that the relevant subjective sleep impairments reported during the first wave could have relied on subtle sleep disruptions that were undetected by the few objective sleep studies from the same period. Taken together with sleep data on previous phases of the pandemic, our findings show that the detrimental effects on sleep determined by the initial pandemic outbreak have not abated across the subsequent waves of contagion, and highlight the need for interventions addressing sleep health in global emergencies.

The relationship between objective and subjective sleep quality is still debated. Here, we investigate differences in objective sleep parameters in habitual subjective good sleepers and bad sleepers with the aim of evaluating sleep continuity, stability and organization as possible determinants of subjective sleep quality. In total, 38 subjects (good sleepers, N = 18; bad sleepers, N = 20) underwent two nights of sleep recording. Traditional sleep parameters displayed no between-groups differences. Conversely, bad sleepers showed lower sleep continuity (awakenings frequency), stability (e.g. arousals and state transitions frequency) and organization (e.g. number of sleep cycles and time spent in cycles). Our findings point to the involvement of these measures in determining habitual sleep quality perception and suggest the possibility to include them in standard sleep assessments.