By Margarita Nahapetyan
People who wake up late in the morning get tired less quickly and have better mental stamina compared to early birds who are wide awake at the crack of dawn, reports a new study that focused on reaction and ability to concentrate of night owls and morning larks.
Early birds wake up by 4 or 5 a.m. and have a hard time to stay alert and productive in the evening. Night owls perform well in the evening but are worth for nothing if forced to wake up too early in the morning. According to scientists, "morning" people experience "a faster build-up of homeostatic sleep pressure" throughout the day compared to night owls, who just seem to resist the pressure to sleep. And after waking up, morning larks usually experience a faster dissipation of the sleep pressure, feeling restored more quickly than night owls. However, after conducting their new study, the scientists now came up with some interesting differences between the brain-activity patterns of the two types of individuals that underlie the differences in behavior.
Scientists led by Philippe Peigneux, a professor of clinical neuropsychology at the Free University of Brussels, along with co-author Christina Schmidt of the University of Liege in Belgium, conducted an experiment in which, using magnetic resonance imaging, they measured alertness and attention times in 30 volunteers. Among subjects, who were asked to spend 2 consecutive nights in a sleep laboratory, were 15 naturally extreme late risers and 16 extreme early risers. The early risers got up between 5 a.m. and 6 a.m., and the late risers were up around noon. The investigators also took hourly saliva samples in order to measure the sleepers' levels of melatonin, a hormone which is in charge of sleep cycles.
The participants in both groups were allowed to stay on their preferred sleep schedules, but each group was awake for the same number of hours each day. For example, if morning larks were waking up at 7 a.m., night volunteers were in bed until 11 a.m., if morning larks were ready to go to sleep at 11 p.m., night owls had to stay up till 3 in the morning.
The results showed that both groups did similarly well at the morning task an hour and a half after getting up. All participants had the same scores on tests that required them to pay attention to a task. However, 10 hours after waking, morning larks showed reduced activity in brain areas linked to attention compared with the night owls who shone, being both quicker and alert at task. So even though volunteers in both groups were sleeping and waking according to their regular schedule, night owls generally outlasted early birds in how long they could stay awake and mentally alert before becoming mentally exhausted. The fMRI supported the behavioral results: 10.5 hours after waking up, the morning larks had less activity in a region deep in the brain involved in the so-called circadian master clock, which regulates our daily cycles of alertness.
Circadian hormones, which keep people alert while awake, can get overridden by sleep pressure, a physiological pull that causes state of sleeplessness the longer individuals are awake. But while people who wake up late seem to cope with sleep pressure in a better way, the late-to-bed strategy might backfire outside the lab, noted Philippe Peigneux. "Morning types may be at an advantage, because their schedule is fitting better with the usual work schedule of the society," he said. "It may represent a problem for evening types obliged to wake up early while having difficulties going to bed in the evening, eventually leading to a sleep debt."