
-                Exposure to noise at night can suppress immune function even if                the sleeper doesn’t wake. Unfamiliar noise, and noise during the                first and last two hours of sleep, has the greatest disruptive effect                on the sleep cycle.
- Teenagers need as much sleep as small children (about 10 hrs) while those over 65 need the least of all (about six hours). For the average adult aged 25-55, eight hours is considered optimal
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