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Actimetry-derived indices and effect of age and napping on the 24-h sleep-wake cycle

Mathilde Reyt1*, Alizée Latteur1, Micheline Maire2, 3, 4, Carolin Reichert2, 3, Christian Cajochen2, 3, Christina Schmidt1, 5, Vincenzo Muto1 and Grégory Hammad1
  • 1 GIGA-CRC in Vivo Imaging, Belgium
  • 2 Centre for Chronobiology, Psychiatric Hospital of the University of Basel, Switzerland
  • 3 Transfaculty Research Platform Molecular and Cognitive Neurosciences, University of Basel, Switzerland
  • 4 Institute of Primary Health Care (BIHAM), University of Bern, Switzerland
  • 5 Research unit of Psychology & Neuroscience of Cognition, Department of Psychology, University of Liège, Belgium

Introduction: Sleep appears as a protective factor in models of cognitive and brain aging. However, temporal organisation of sleep and wakefulness over the 24-hour cycle still remains underestimated in these models. Chronic napping is frequent in the older population and might interfere with sleep-wake regulation. Here, we explored age-related changes in actimetry-derived indices of both sleep and sleep-wake fragmentation. Methods: Actimetry data (Actiwatch plus device, Cambridge Neurotechnology) were collected in 24 younger (20-32 years, 16 women) and 37 older participants (57-85 years, 18 women, 20 chronic nappers [naps > 20 min/day, > 3*week, since >1 year]). Periods of complete inactivity > 2 hours were excluded from analyses since the latter presumably reflect actigraph removal. Sleep-wake fragmentation was explored by estimating transition probability to rest during daytime (kAR), transition probability into activity during night-time (kRA), volume of sleep in the afternoon (fSOD), intra-daily variability (IV) and inter-daily stability (IS). A composite score of executive functions (Miyake et al. 2000) was calculated for older participants. Results: Significant age-related changes were observed for indices measuring sleep-wake cycle fragmentation (IV, t(59)= -4.51, p < 0.001), wake fragmentation (kAR, t(59)= -2.75, p < 0.01, fSOD, t(59)= -2.36, p < 0.05) and inter-daily stability (IS, t(59)= -2.32, p > 0.05). The younger presented lower wake fragmentation compared to both older no-nappers (kAR, t(39)= -2.33, p < 0.05) and nappers (kAR, t(42)= -2.07, p < 0.05, fSOD, t(42)= -2.98, p < 0.01). Furthermore, sleep-wake cycle fragmentation was lower in younger participants compared to older nappers only (IV, t(42)= -5.21, p < 0.001). Compared to older no-nappers, older nappers presented higher sleep-wake cycle fragmentation (IV, t(35) = -2.49, p < 0.05) and higher wake fragmentation (fSOD, t(35) = 2.50, p < 0.05). Moreover, this higher wake fragmentation is related to lower score of executive functions (p < 0.05). Conclusions: Overall, our data suggest that the impact of age is evident in actimetry-derived indices taking into account wake fragmentation (ie intrusion of rest periods at daytime) in addition to night-time sleep fragmentation. Nappers presented higher sleep-wake cycle fragmentation and wake fragmentation compared to no-nappers, while sleep fragmentation did not significantly differ. In this two groups, a wake-fragmentation index (fSOD) is correlated to the score of executive functions. Future analyses aim at taking into account individually-tailored rest-activity profiles to estimate sleep-wake cycle fragmentation. Finally, whether these indices explain significant part of variance in cognitive ageing remains to be assessed. Summary: The frequency of chronic napping increases in the older population and might interfere with sleep-wake regulation. The latter is tuned to alternate between a state of rest during night-time and a wake period during daytime. We explored age-related changes in actimetry-derived indices of sleep-wake cycle fragmentation, wake fragmentation and sleep fragmentation. Nappers presented higher sleep-wake cycle fragmentation and wake fragmentation compared to no-nappers, while sleep fragmentation did not significantly differ. A wake-fragmentation index is correlated to performances of executive functions. Our data suggest that the impact of age is evident in actimetry-derived indices taking into account wake fragmentation during daytime.

Acknowledgements

Sources of funding: Swiss National Foundation (SNF), Belgian Fund for Scientific Research (FNRS), European Research Council (ERC-Starting Grant).

References

Miyake, A. et al., The unity and diversity of executive functions and their contributions to complex “frontal lobe” tasks: a latent variable analysis. Cognitive Psychology, 2000. 41: p.49-100.

Keywords: Actimetry, age, napping, sleep-wake cycle, Sleep fragmentation index

Conference: Belgian Brain Congress 2018 — Belgian Brain Council, LIEGE, Belgium, 19 Oct - 19 Oct, 2018.

Presentation Type: e-posters

Topic: NOVEL STRATEGIES FOR NEUROLOGICAL AND MENTAL DISORDERS: SCIENTIFIC BASIS AND VALUE FOR PATIENT-CENTERED CARE

Citation: Reyt M, Latteur A, Maire M, Reichert C, Cajochen C, Schmidt C, Muto V and Hammad G (2019). Actimetry-derived indices and effect of age and napping on the 24-h sleep-wake cycle. Front. Neurosci. Conference Abstract: Belgian Brain Congress 2018 — Belgian Brain Council. doi: 10.3389/conf.fnins.2018.95.00101

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Received: 31 Aug 2018; Published Online: 17 Jan 2019.

* Correspondence: PhD. Mathilde Reyt, GIGA-CRC in Vivo Imaging, Liège, Belgium, mathilde.reyt@gmail.com