Article

Age-related reduction in daytime sleep propensity and nocturnal slow wave sleep

Surrey Sleep Research Centre, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK.
Sleep (Impact Factor: 5.06). 02/2010; 33(2):211-23.
Source: PubMed

ABSTRACT To investigate whether age-related and experimental reductions in SWS and sleep continuity are associated with increased daytime sleep propensity.
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).
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 8.7 min (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).
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.

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    • "With advancing age sleep becomes more fragmented and “lighter” due to increased percentage of stage one sleep and decreased percentage of slow wave sleep [29]. It has been shown that there is an age-related reduction in sleep duration and depth required to maintain daytime alertness [30] and that reduced night-time sleep quality in older people does not cause increased daytime sleep propensity [31]. These changes appear to be, at least in part, related to an age-related reduction in the homeostatic drive for sleep and a reduced strength of the circadian signal [32]. "
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