As a person ages, their circadian clock begins to slow down. But a study of nearly 150 human brains suggests that’s also when a new biological clock kicks in.
A 24-hour circadian rhythm controls nearly all brain and body processes, such as the sleep/wake cycle, metabolism, alertness, and cognition. These daily activity patterns are regulated by certain genes that are found in almost all cells, but have rarely been studied in the human brain.
“Studies have reported that older adults tend to perform complex cognitive tasks better in the morning and get worse through the day,” says Colleen McClung, associate professor of psychiatry at the University of Pittsburgh School of Medicine. “We know also that the circadian rhythm changes with aging, leading to awakening earlier in the morning, fewer hours of sleep, and less robust body temperature rhythms.”