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Many CRONies report needing less sleep, and the literature seems to suggest reduced sleep among CR'ed animals. There has been nagging concern among some CRONies that we may be harming ourselves, based on the belief that humans need around 8h of sleep to be healthy and operate effectively.

This study posted by Dean (2004-02-11), as well as several others it references, seem to suggest less than 8h sleep may in fact be optimal from a longevity perspective. Comforting news for CRONies.

Many CRONies report reduced sleep, often without any apparent reduction in
alertness or increase in fatigue. We just seem to need less sleep. This may
have an evolutionary basis. One role of sleep may have been to reduce our
nighttime activity level, to avoid detection by predators. In times of
scarcity, the survival benefit of additional food gathering time may have
outweighed the advantages of "lying low". Hence, CR'ed animals may have a
built in tendency to sleep less when food is scarce. In addition to the
anecdotal evidence from CRONies, there is evidence in the literature that CR
tends to reduce sleep (e.g. [3] and [4])

There has been some concern that this reduced sleep in CRONies may not be
healthy. The belief that we need 8 hours of sleep to be healthy and function
at peak efficiency is deeply ingrained.

This new study [1] in the Journal of Sleep lends further support to the idea
that 7h or less sleep is just fine and perhaps better than 8h from a
mortality perspective:

"... Sleep duration of shorter or longer than 7 hours was associated with a
significantly elevated risk of all-cause mortality. However, the significant
association with short sleep disappears when adjusted for some covariates
among men. ... Sleep duration at night of 7 hours was found to show the
lowest mortality risk."

The accompanying editorial [2] was even more interesting:

"The JACC study from Japan, reported in this issue of SLEEP by Tamakoshi,
Ohno, and colleagues suggested:
1) The best survival is experienced by those who sleep 6.5-7.5 hours
on weekdays.
2) The mortality risk of those who sleep more than 7.5 hours is of
more concern than the risk of those who sleep less than 6.5 hours.
Even those who reported sleeping 8 hours had greater mortality risk
than those who slept an hour less."

And further:

"Although these conclusions might surprise clinicians, the JACC data
are fully consistent with recently-reported results from the Nurses'
Health Study (NHS) and the Cancer Prevention Study II (CPSII).
The consistency of results among these three enormous studies, conducted
with varying methodologies on two continents and over two
decades, suggests that they are likely to prove reliable. A dozen smaller
studies have supported the general findings of the large studies. No
persuasive
epidemiologic evidence contradicts them."

The bottom line appears to be if one is functioning well, one shouldn't
worry if one is getting less sleep than was formerly considered normal or
necessary.

Take care!

--Dean

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[1] SLEEP 2004;27(1):51-4.

Self-Reported Sleep Duration as a Predictor of All-Cause Mortality: Results
from the JACC Study, Japan

Akiko Tamakoshi, MD, PhD; Yoshiyuki Ohno, MD, MPH, PhD

Abstract: http://www.journalsleep.org/citation/sleepdata.asp?citationid=2317

... A total of 104,010 subjects (43,852 men and 60,158 women), aged 40 to 79
years, ... were followed for an average of 9.9 years. ...

Results:
... Sleep duration of shorter or longer than 7 hours was associated with a
significantly elevated risk of all-cause mortality. However, the significant
association with short sleep disappears when adjusted for some covariates
among men.

Conclusions:
Sleep duration at night of 7 hours was found to show the lowest mortality
risk.

PMID: Not available

---------------
[2] SLEEP 2004;27(1):51-4.

Do We Sleep Too Much? Comment on Tamakoshi A; Ohno Y. Self-reported sleep
duration as a predictor of all-cause mortality: results from the JACC study,
Japan.

Daniel F. Kripke, M.D.

Free Full Text: http://www.journalsleep.org/Editorials2004/SleepTooMuch.pdf

PMID: Not available

---------------
[3] Neurobiol Aging. 2002 Sep-Oct;23(5):771-6.

Effects of hypocaloric diet on sleep in young and old rats.

Salin-Pascual RJ, Upadhyay U, Shiromani PJ.

Aging produces a loss in a number of behavioral and cognitive functions,
including sleep. Hypocaloric diet is one of the few methods that have been
shown to retard the effects due to age. However, the effects of such a diet
on sleep have never been investigated. In the present study, 21 months old
male F344 rats fed a 60% calorie-reduced diet continued to have a
significant reduction in delta power (0.3-4 Hz EEG), less sleep following 12
h total sleep deprivation (TSD) and increased sensitivity to caffeine
compared to young rats (3 months) fed a similar diet. These results indicate
that caloric restriction is unable to prevent the decline in sleep that
occurs with aging. Copyright 2002 Elsevier Science Inc.

PMID: 12392780

---------------
[4] Am J Clin Nutr. 1994 Feb;59(2):346-9

Restricted energy intake affects nocturnal body temperature and sleep
patterns.

Karklin A, Driver HS, Buffenstein R.

Department of Physiology, University of the Witwatersrand Medical School,
Johannesburg, South Africa.

Changes in nocturnal body temperature, sleep patterns, and blood variables
with energy restriction (3347 kJ/d) were studied in nine overweight (body
mass index 26.1 +/- 2.8) premenopausal women aged 20-36 y. Variables were
measured both 2 wk before and in the final 2 wk of 4-wk dieting. Data
collected 28 d apart were compared to attenuate menstrual cycle differences.
Subjects lost 8 +/- 4% of their initial body mass after 4 wk of energy
restriction and plasma triiodothyronine (T3) was significantly reduced from
5.9 +/- 0.7 to 5.1 +/- 0.6 pmol/L (P < 0.05). The implied suppression of
heat production (metabolic rate) with reduced T3 may account for the
observed decrease in minimum nocturnal rectal temperature (from 36.5 +/- 0.3
to 36.3 +/- 0.3 degree C, P < 0.05). Furthermore, dieting significantly
altered sleep patterns; sleep onset latency was lengthened and slow-wave
sleep decreased (P < 0.05). These changes may be indicative of reduced
restorative/biosynthetic requirements. It thus appears that energy
restriction results in a hypometabolic state that affects nocturnal body
temperature and sleep patterns.

PMID: 8310984