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Age-Related Reduction in Daytime Sleep Propensity and Nocturnal Slow Wave Sleep

in
Publisher: 
Journal SLEEP
Author: 
Derk-Jan Dijk, PhD1; John A. Groeger, PhD1,2; Neil Stanley, PhD1; Stephen Deacon, PhD3
Date published: 
4 February, 2010
Region: 
United Kingdom

Publication type: 
research
Publication link: 
Age-Related Reduction in Daytime Sleep Propensity and Nocturnal Slow Wave Sleep
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1Surrey Sleep Research Centre, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK; 2Department of Psychology, University of Surrey, Guildford, UK; 3H. Lundbeck A/S, Denmark and Lundbeck Ltd, UK

SLEEP 2010;33(2):211-223.

Objective: To investigate whether age-related and experimental reductions in SWS and sleep continuity are associated with increased daytime sleep propensity.

Methods: Assessment of daytime sleep propensity under baseline conditions and following experimental disruption of SWS. Healthy young (20-30 y, n = 44), middle-aged (40-55 y, n = 35) and older (66-83 y, n = 31) men and women, completed a 2-way parallel group study. After an 8-h baseline sleep episode, subjects were randomized to 2 nights with selective SWS disruption by acoustic stimuli, or without disruption, followed by 1 recovery night. Objective and subjective sleep propensity were assessed using the Multiple Sleep Latency Test (MSLT) and the Karolinska Sleepiness Scale (KSS).

Findings: During baseline sleep, SWS decreased (P < 0.001) and the number of awakenings increased (P < 0.001) across the 3 age groups. During the baseline day, MSLT values increased across the three age groups (P < 0.0001) with mean values of 8.7min (SD: 4.5), 11.7 (5.1) and 14.2 (4.1) in the young, middle-aged, and older adults, respectively. KSS values were 3.7 (1.0), 3.2 (0.9), and 3.4 (0.6) (age-group: P = 0.031). Two nights of SWS disruption led to a reduction in MSLT and increase in KSS in all 3 age groups (SWS disruption vs. control: P < 0.05 in all cases).

Conclusions: Healthy aging is associated with a reduction in daytime sleep propensity, sleep continuity, and SWS. In contrast, experimental disruption of SWS leads to an increase in daytime sleep propensity. The age-related decline in SWS and reduction in daytime sleep propensity may reflect a lessening in homeostatic sleep requirement. Healthy older adults without sleep disorders can expect to be less sleepy during the daytime than young adults.

Keywords: Aging, insomnia, slow wave sleep, sleepiness, alertness

 

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