Circadian Rhythms

The circadian timing system is a major organizing feature of human physiology and behavior. Great progress in understanding the molecular and genetic basis of circadian rhythmicity in mammals was made in the 1990s. While it was once hypothesized that age-related changes in the circadian timing system led to an increase in disorders of sleep timing with age, recent studies have indicated that many aspects of circadian rhythmicity are not significantly different between young and healthy older individuals. There are, however, age-related changes in sleep, and also age-related changes in the interaction between the timing of sleep and the output of the circadian pacemaker, resulting in age-related sleep disruption in the latter half of the night. While the neurobiological basis of age-related changes in the interaction between sleep and circadian rhythmicity are not yet known, continued research promises better understanding of how these systems change with age and how knowledge of such changes can lead to development of chronobiological treatment for age-related sleep disruption.