|dc.description.abstract||Daytime napping improves well-being and performance for young adults. The benefits
of napping in older adults should be investigated because they have fragmented nocturnal
sleep, cognitive declines, and more opportunity to nap. In addition, experience with napping
might influence the benefits of napping.
Study 1 examined the role of experience with napping in young adults. Habitual (n =
23) and non-habitual nappers (n = 16) were randomly assigned to a 20-minute nap or a 20-
minute reading condition. Both groups slept the same according to macro architecture.
However, microarchitecture showed greater theta, alpha, and beta power during Stage 1, and
greater delta, alpha, and sigma power during Stage 2 for habitual nappers, for the most part
indicating better sleep. Both groups felt less sleepy after the nap. P2 latency, reflecting
information processing, decreased after the nap for habitual nappers, and after the control
condition for non-habitual nappers. In sum, both groups who slept felt better, but only the
habitual nappers who napped gained a benefit in terms of information processing. Based on
this outcome, experience with napping was investigated in Study 2.
Study 2 examined the extent to which daytime napping enhanced cognition in older
adults, especially frontal lobe function. Cognitive deficits in older adults may be due to sleep
loss and age-related decline in brain functioning. Longer naps were expected to provide greater
improvement, particularly for older adults, by reducing sleep pressure.
Thirty-two adults, aged 24-70 years, participated in a repeated measures dose-response
manipulation of sleep pressure. Twenty- and sixty-minute naps were compared to a no-nap
condition in three age groups. Mood, subjective sleepiness, reaction time, working memory,
novelty detection, and waking electro physiological measures were taken before and after each
condition. EEG was also recorded during each nap or rest condition.
Napping reduced subjective sleepiness, improved working memory (serial addition /
subtraction task), and improved attention (reduced P2 amplitude). Physiological sleepiness
(i.e., waking theta power) increased following the control condition, and decreased after the
longer nap. Increased beta power after the short nap, and seen with older adults overall, may
have reflected increased mental effort.
Older adults had longer latencies and smaller amplitudes for several event-related
potential components, and higher beta and gamma power. Following the longer nap, gamma
power decreased for older adults, but increased for young adults. Beta and gamma power may
represent enhanced alertness or mental effort. In addition, Nl amplitude showed that benefits
depend on the preceding nap length as well as age. Since the middle group had smaller Nl
amplitudes following the short nap and rest condition, it is possible that they needed a longer
nap to maintain alertness. Older adults did not show improvements to Nl amplitude following
any condition; they may have needed a nap longer than 60 minutes to gain benefits to attention
or early information processing. Sleep characteristics were not related to benefits of napping.
Experience with napping was also investigated. Subjective data confirmed habitual
nappers were happier to nap, while non-habitual nappers were happier to stay awake,
reflecting self-identified napping habits. Non-habitual nappers were sleepier after a nap, and
had faster brain activity (i.e., heightened vigilance) at sleep onset. These reasons may explain
why non-habitual nappers choose not to nap.||en_US