PerspectiveCircadian Rhythms

A Clock for the Ages

Science  25 Jun 1999:
Vol. 284, Issue 5423, pp. 2102-2103
DOI: 10.1126/science.284.5423.2102

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It is well known that as we age, we need fewer hours of sleep and wake up much earlier in the morning. This change has been attributed to a shortening of the period of the human circadian pacemaker. However, Robert Moore explains in a Perspective that new findings ( Czeisler et al.) demonstrate that it is not the pacemaker itself that is altered but rather the way it is entrained to the day-night cycle. The period of the circadian pacemaker is very similar (24.2 hours) in both young and old people, suggesting that this is one physiological function that does not alter with aging.