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The tendency to sleep at a particular time each day defines an individual’s “chronotype”. Although profoundly influenced by genetics and light exposure, age-related body changes play a key role.
Puberty heralds a notable shift as bedtimes and wake times get later. This trend continues until 19.5 years in women and nearly 21 in men. Then it gradually reverses. By 55 we wake at around the time we did as young children, approximately two hours earlier than as adolescents. So a 7 am alarm call for a teenager is equivalent
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