The Effects of Pre-Sleep Learning on Sleep Continuity, Stability, and Organization in Elderly Individuals

Abstract

Several studies have consistently shown that pre-sleep learning is associated to changes of sleep structure. Whereas previous research has mainly focused on sleep states, namely REM and NREM amount, very little attention has been paid to the hypothesis that pre-sleep learning might improve sleep continuity, stability, and cyclic organization, which are often impaired in aging. Thus, aim of this research was to assess, in a sample of 18 healthy elderly subjects, whether a memory task administered at bedtime would determine changes in any sleep parameter, with special regard to sleep continuity, stability, and organization. To this purpose, a baseline sleep (BL), i.e., a normal sleep with 9-h time in bed (TIB), was compared to a post-training sleep (TR), with the same TIB but preceded by an intensive training session. For the latter, a verbal declarative task was used, consisting in learning paired-word lists, rehearsed, and recalled for three times in a row. To control for individual learning abilities, subjects were administered several sets of lists with increasing difficulty, until they reached an error rate ≥20% at third recall. Relative to BL, TR shows a significant reduction in the frequency of brief awakenings, arousals, state transitions, “functional uncertainty” (FU) periods, and in the percentage of time in FU over total sleep time (TST). A significant increase in the number of complete cycles, total cycle time (TCT), and TCT/TST proportion was also found. All these changes are evenly distributed over the sleep episode. No sleep stage measure display significant changes, apart from a slight reduction in the percentage of Stage 1. Scores at retest are negatively correlated with both the frequency of arousals and of state transitions. Our data suggest that pre-sleep learning can yield a beneficial re-organizing effect on elderlies’ sleep quality. The inverse correlation between recall scores and the measures of sleep continuity and stability provides further support to the role of these features in memory processes.

Sleep Measures Expressing ‘Functional Uncertainty' in Elderlies' Sleep

“…In conclusion, the previously cited evidence [67] that sleep continuity, stability and organization measures, compared to the classical ones, might be more sensible to cognitive activity during wake and may better discriminate elderlies' sleep from the young adults', together with their high specificity and manageability, encourages to include them in standard sleep assessments on both aged and sleep-disordered populations as specific sleep quality indexes.…”

“…With respect to the aged population, Mazzoni et al [66] for instance showed that average duration of NREM-REM cycles and TCT are highly correlated with recall at awakening of word lists learned before sleep. More recently, with the aim of investigating post-learning sleep changes in elderly subjects, we have administered a paired-word lists task to a group of healthy old adults (aged >65 years) at bedtime [67]. Interestingly, we found significant increases in post-training sleep of all continuity, stability and cyclic organization measures, whereas we did not report any change in classical sleep measures such as TST, stage 2 sleep, SWS and REM sleep proportions.…”

Sleep, Cognition, and Normal Aging

“…Nevertheless, some work has connected overnight retention of episodic memories to spindle density (Seeck-Hirschner et al, 2012) and ability to maintain sleep (i.e., few awakenings; Conte, Carobbi, Errico, & Ficca, 2012; Mazzoni et al, 1999). Others have failed to observe correlations with spindles (and sigma spectral power; Hornung et al, 2007, 2009; C. Westerberg, personal communication, July 22, 2013) or reported a positive correlation between retention and time awake at night (Seeck-Hirschner et al, 2012).…”

Sleep and Cognition in the Elderly

“…In this respect, this issue addresses changes in sleep and circadian rhythms in the elderly, and how they impact on cognitive performance and brain activity (Schmidt et al, 2012). Sleep-dependent memory consolidation and the age-related changes that may compromise this complex process are also discussed (Harand et al, 2012), as well as how pre-sleep learning can improve sleep continuity, stability, and organization in older adults (Conte et al, 2012). Considering mental productions during sleep, variations in dream recall frequency, and dream theme diversity across the lifespan are also investigated (Nielsen, 2012).…”