Ordinary household lighting makes it harder to get up in the morning because it resets the body’s internal clock, a study suggests.
While scientists long have known that bright light can reset the brain’s internal clock, which governs such things as the drive to sleep, the new work shows that ordinary indoor lighting also can affect the setting.
Results suggest that when people are exposed to indoor lighting after sunset, the body’s clock is reset in such a way that, on average, the peak drive for sleep occurs at about 4 a.m. to 5 a.m. Without artificial lighting, that peak probably would occur about midnight, said the study’s researcher, Dr. Charles Czeisler.
As a result of the shift in their internal clocks, Czeisler said, people exposed to indoor light must wake up much closer to the time when their bodies are making peak demands for sleep.
He said that makes it harder to get out of bed in the morning and also makes it harder to go to sleep early enough the next night to get enough rest.