Sex Sleep Eat Drink Dream (38 page)

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But scientists suspect that the switch:
C. S. Colwell and'S. Michel, "Sleep and circadian rhythms: do sleep centers talk back to the clock?,"
Nature Neuroscience
6:10, 1005–6 (2003); T. Deboer et al., "Sleep states alter activity of suprachiasmatic nucleus neurons,"
Nature Neuroscience
6:10, 1086–90 (2003); D. J. Dijk and C. A. Czeisler, "Contribution of the circadian pacemaker and the sleep homeostat to sleep propensity, sleep structure, electroencephalographic slow waves, and sleep spindle activity in humans,"
Journal of Neuroscience
15, 3526–38 (1995).
When sleep seized my daughter:
The following description of sleep stages draws from Dement and Vaughan,
The Promise of Sleep,
18–22; Peretz Lavie,
The Enchanted World of Sleep
(New Haven: Yale University Press, 1996), 26 f; J. M. Siegel, "Why we sleep,"
Scientific American,
November 2003, 92–97.

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When scientists implanted tiny sensors:
K. J. Noonan, "Growing pains: are they due to increased growth during recumbency as documented in a lamb model?,"
Journal of Pediatric Orthopaedics
24, 6 (2004).
When Swiss researchers studied a gene:
J. V. Retey et al., "A functional genetic variation of adenosine deaminase affects the duration and intensity of deep sleep in humans,"
Proceedings of the National Academy of Sciences
102, 15676–81 (2005).
but a complex system of neurotransmitters:
J. M. Siegel, "Clues to the functions of mammalian sleep,"
Nature
437, 1264–71 (2005).

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Everyone dreams, says J. Allan Hobson:
Hobson, "Sleep is of the brain, by the brain, and for the brain."
Recent advances in imaging:
Siegel, "Why we sleep."
Lively are the cortical regions:
T. A. Nielsen and P. Stenstrom, "What are the memory sources of dreaming?,"
Nature
437, 1286–89 (2005).
nightmares may in some cases arise:
T. Nielsen, "Chronobiological features of dream production,"
Sleep Medicine Reviews
8, 403–24 (2004).

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women typically have more nightmares:
T. A. Nielsen, "The typical dreams of Canadian university students,"
Dreaming
13:4, 211 (2003).
"
This gender difference is quite robust":
Tore Nielsen, personal communication, September 2006.
"
REM
dreams tend to be forgotten":
A. Rechtschaffen, personal communication, February 11, 2005.

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but it does tend to improve sleep patterns:
S. D. Youngstedt and C. E. Kline, "Epidemiology of exercise and sleep,"
Sleep and Biological Rhythms
4:3, 215 (2006); see also'S. D. Youngstedt et al., "No association of sleep with total daily physical activity in normal sleepers,"
Physiology and Behavior
78, 395–401 (2003); S. D. Youngstedt, "Does exercise truly enhance sleep?,"
Physician and Sports Medicine
25:10, 72–82 (1997).
Researchers recently glimpsed why:
J. Mu et al., "Ethanol influences on native T-type calcium current in thalamic sleep circuitry,"
Journal of Pharmacology and Experimental Therapy
307:1, 197–204 (2003).

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 "
If sleep does not serve":
A. Rechtschaffen and B. M. Bergmann, "Sleep deprivation in the rat: an update of the 1989 paper,"
Sleep
25, 18–24 (2002).
William Dement, who observed him:
Dement and Vaughan,
The Promise of Sleep,
245.
"
There's another long-term, massive experiment":
This and the following quotes from Charles Czeisler are from C. Czeisler, "Sleep: what happens when doctors do without it?," Medical Center Hour, University of Virginia, March 1, 2006.
A 2005 poll taken by the National Sleep Foundation:
www.sleepfoundation.org/press/index.php?secid=&id=120.

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As recently as a decade ago, eminent researchers:
Lavie,
The Enchanted World of Sleep,
114; C. A. Czeisler, "Quantifying consequences of chronic sleep restriction,"
Sleep
26:3, 247–48 (2003); H.P.A. Van Dongen et al., "The cumulative cost of additional wakefulness,"
Sleep
26:2, 117 (2003).

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just how much sleep is best:
See D. F. Kripke et al., "Mortality associated with sleep duration and insomnia,"
Archives of General Psychiatry
59, 131–36 (2002).
people who slept less than six hours a night:
Van Dongen et al., "The cumulative cost of additional wakefulness."
in terms of sedative effects:
T. Roehrs et al., "Ethanol and sleep loss: a 'dose' comparison of impairing effects,"
Sleep
26:8, 981–85 (2003); D. Dawson and K. Reid, "Fatigue, alcohol and performance impairment,"
Nature
388, 235 (1997).
"
With one night of short sleep":
Czeisler, "Sleep: what happens when doctors do without it?"; L. K. Barger et al., "Extended work shifts and the risk of motor vehicle crashes among interns,"
New England Journal of Medicine
352, 125–34 (2005).
When you're driving ... at sixty:
Dement and Vaughan,
The Promise of Sleep,
218.
drowsiness increases a driver's risk:
"Breakthrough research on real-world driver behavior released," press release, April 20, 2006,
www.nhtsa.gov
; editorial page,
Nature Insight: Sleep
437, 1206 (2005).

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As William Dement points out:
Dement and Vaughan,
The Promise of Sleep
, 51–53; Russell Foster and Leon Kreitzman,
Rhythms of Life
(London: Profile Books, 2004), 208–9.
The report on the disaster:
http://history.nasa.gov/rogersrep/v2appg.htm
#g25.
scientists relied on subjects' self-reported:
Czeisler, "Quantifying consequences of chronic sleep restriction."
To parse the popular belief:
K. Spiegel et al., "Effect of sleep deprivation on response to immunization,"
Journal of the American Medical Association
288:12, 1471–72 (2002).
Van Cauter also found that sleep loss:
K. Spiegel et al., "Impact of sleep debt on metabolic and endocrine function,"
Lancet
354, 1435–39 1999); E. Tasali, "Slow wave activity levels are correlated with insulin secretion in healthy young adults,"
Sleep
26 (abstract supp.), A62 (2003).

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She and her team have reported:
K. Spiegel et al., "Brief communication: sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite,"
Annals of Internal Medicine
141, 846–50 (2004); see also K. Spiegel, "Sleep curtailment results in decreased leptin levels and increased hunger and appetite,"
Sleep
26 (abstract supp.), A174 (2003).
obesity is tightly correlated:
J. E. Gangwisch et al., "Inadequate sleep as a risk factor for obesity: analyses of the NHANES I,"
Sleep
28:10, 1217–20 (2005). For a similar study of children, see J.-P. Chaput et al., "Relationship between short sleeping hours and childhood overweight/obesity: results from the 'Quebec en Forme' Project,"
International Journal of Obesity,
30:7, 1080–85 (2006).
A twist to this tale comes:
report presented by Sanjay Patel at the American Thoracic Society international conference, May 23, 2006, San Diego.

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 "
The effects of sleep deprivation alone":
A. Rechtschaffen and B. M. Bergmann, "Sleep deprivation in the rat: an update of the 1989 paper,"
Sleep
25, 18–24 (2002); personal communication with Rechtschaffen, February 16, 2005.
Jerry Siegel and others have delved:
The following discussion comes from J. M. Siegel, "Clues to the functions of mammalian sleep,"
Nature
437, 1264–71 (2005); Siegel, "The phylogeny of sleep"; Siegel, "Why we sleep."

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Siegel suspects that one key:
Siegel, "Clues to the functions of mammalian sleep"; J. M. Siegel and M. A. Rogawski, "A function for
REM
sleep: regulation of noradrenergic receptor sensitivity,"
Brain Research Review
13, 213–33 (1988).

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REM
steps in to keep neurons:
M. J. Morrissey, "Paradoxical sleep and its role in the prevention of apoptosis in the developing brain,"
Sleep
26 (abstract supp.), A46 (2003).
a group of Finnish researchers:
M. Cheour et al., "Speech sounds learned by sleeping newborns,"
Nature
415, 599–600 (2002).

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Robert Stickgold and his colleagues:
R. Stickgold et al., "Visual discrimination learning requires sleep after training,"
Nature Neuroscience
3, 1237–38 (2000); M. P. Walker et al., "Practice with sleep makes perfect: sleep-dependent motor skill learning,"
Neuron
35, 205–11 (2002).
Some years ago, scientists found:
P. Maquet et al., "Experience-dependent changes in cerebral activation during rem sleep,"
Nature Neuroscience
3:8, 831–36 (2000).
One recent study showed that the precise:
P. Peigneux et al., "Are spatial memories strengthened in the human hippocampus during slow-wave sleep?,"
Neuron
44, 535–45 (2004).
Perhaps sleep allows the brain:
I. S. Hairston and R. R. Knight, "Sleep on it,"
Nature
430, 27–28 (2004).
Tononi and his colleagues reported:
R. Huber et al., "Local sleep and learning,"
Nature
430, 78–81 (2004).
A team led by Ullrich Wagner:
U. Wagner et al., "Sleep inspires insight,"
Nature
427, 352–55 (2004).

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The annals of literature:
Lavie,
The Enchanted World of Sleep,
90.
Robert Louis Stevenson claimed:
Lavie,
The Enchanted World of Sleep,
90; James Pope Hennessy,
Robert Louis Stevenson
(New York: Simon and Schuster, 1975), 207; quote from Stevenson,
Across the Plains,
http://sunsite.berkeley.edu/literature/stevenson/plains/plains8.html.
Science also holds stories:
Lavie,
The Enchanted World of Sleep,
90; Paolo Mazzarello, "What dreams may come,"
Nature
408, 523 (2000); Dement and Vaughan,
The Promise of Sleep,
321.

13. HOUR OF THE WOLF

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When William Dement and Mary Carskadon studied:
M. A. Carskadon et al., "Sleep and daytime sleepiness in the elderly,"
Journal of Geriatric Psychiatry
13:2, 135–51 (1980); R. M. Coleman et al., "Sleep-wake disorders in the elderly: polysomnographic analysis,"
Journal of the American Geriatric Society
27:9, 289–96 (1981); William C. Dement and Christopher Vaughan,
The Promise of Sleep
(New York: Dell, 2000), 121; see also D. J. Dijk et al., "Age-related increase in awakenings: impaired consolidation of non-rem sleep at all circadian phases,"
Sleep
24:5, 565–77 (2001).
This loss of deep sleep actually begins in midlife:
E. Van Cauter, "Age-related changes in slow wave sleep and rem sleep and relationship with growth hormone and Cortisol levels in healthy men,"
Journal of the American Medical Association
284, 861–68 (2000).
Some evidence suggests that in the elderly:
J. E Duffy et al., "Later endogenous circadian temperature nadir relative to an earlier wake time in older people,"
American Journal of Physiology
275:5 (part 2), R1478–87 (1998); E. Van Cauter et al., "Effects of gender and age on the levels of circadian rhythmicity of plasma Cortisol,"
Journal of Clinical Endocrinology and Metabolism
81, 2468–73 (1996); T. Reilly et al., "Aging, rhythms of physical performance, and adjustment to changes in the sleep-activity cycle,"
Occupational and Environmental Medicine
54, 812–16 (1997); J. F. Duffy and C. A. Czeisler, "Age-related change in the relationship between circadian period, circadian phase, and diurnal preference in humans,"
Neuroscience Letters
318:3, 117–20 (2002); C. A. Czeisler et al., "Association of sleep-wake habits in older people with changes in output of circadian pacemaker,"
Lancet
340, 933–36 (1992); F. Aujard et al., "Circadian rhythms in firing rate of individual suprachiasmatic nucleus neurons from adult and middle-aged mice,"
Neuroscience
106:2, 255–61 (2001); E. Satinoff, "Patterns of circadian body temperature rhythms in aged rats,"
Clinical and Experimental Pharmacology arid Physiology
25:2, 135–40 (1998).

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They may in part be rooted:
W. N. Charman, "Age, lens transmittance, and the possible effects of light on melatonin suppression,"
Ophthalmic and Physiological Optics
23, 181–87 (2003).
Scientists know that normal aging:
M. D. Madeira et al., "Age and sex do not affect the volume, cell numbers, or cell size of the suprachiasmatic nucleus of the rat: an unbiased stereological study,"
Journal of Comparative Neurology
361:4, 585–601 (1995).
But at least one new study ... suggests that aging:
S. Yamazaki, "Effects of aging on central and peripheral mammalian clocks,"
Proceedings of the National Academy of Sciences
99:16, 10801–6 (2002); F. Aujard et al., "Circadian rhythms in firing rate"; D. E. Kolker, "Aging alters circadian and light-induced expression of clock genes in golden hamsters,"
Journal of Biological Rhythms
18:2, 159–69 (2003).
In traditional, non-Western societies:
C. M. Worthman and M. Melby, "Toward a comparative developmental ecology of human sleep," in M. A. Carskadon, ed.,
Adolescent Sleep Patterns: Biological, Social, and Psychological Influences
(New York: Cambridge University Press), 69–117; personal communication with Carol Worthman, August 8, 2006.