A new study finds that “night owls” — those whose internal body clock dictates they go to bed and wake up very late — appear to have fundamental differences in their brain function compared to “morning larks.”
This suggests that night owls could be disadvantaged by the constraints of a normal working day.
Researchers at the University of Birmingham discovered that night owls, who typically have an average bedtime of 2:30 am and a wake-up time of 10:15 am, have lower resting brain connectivity in many of the brain regions associated with the maintenance of consciousness.
Importantly, this reduced brain connectivity was tied to poorer attention, slower reactions and increased sleepiness throughout the hours of a typical working day.
According to the Office for National Statistics, around 12 percent of employees work night shifts. It is well-established that night-shift workers often face huge negative health consequences due to the constant disruption to sleep and body clocks.
However, this type of disruption can also result from being forced to fit into a societal 9-5 working day if those timings do not align with one’s natural biological rhythms. Since around 40-50 percent of the population identify as having a preference for later bedtimes and for getting up after 8:20 a.m., the researchers say much more work needs to be done to investigate any negative implications for this group.
“A huge number of people struggle to deliver their best performance during work or school hours they are not naturally suited to,” said lead researcher Dr. Elise Facer-Childs, from the University of Birmingham’s Centre for Human Brain Health. “There is a critical need to increase our understanding of these issues in order to minimize health risks in society, as well as maximize productivity.”
For the study, the researchers looked at brain function at rest and linked it to the cognitive abilities of 38 individuals who were identified as either night owls or morning larks using physiological rhythms (melatonin and cortisol), continuous sleep/wake monitoring and questionnaires.
The participants underwent MRI scans and then completed a series of tasks, with testing sessions being undertaken at a range of different times during the day from 8 a.m. to 8 p.m. They were also asked to report on their levels of sleepiness.
Self-identified morning larks reported being least sleepy with their fastest reaction time during the early morning tests, which was significantly better than night owls. Night owls, however, were least sleepy and had their fastest reaction time at 8pm in the evening, although this was not significantly better than the larks, highlighting that night owls are most disadvantaged in the morning.
Interestingly, the brain connectivity in the regions that could predict better performance and lower sleepiness was much higher in larks at all time points, suggesting that the resting state brain connectivity of night owls is impaired throughout the whole day (8 a.m.-8 p.m.).
“This mismatch between a person’s biological time and social time, which most of us have experienced in the form of jet lag, is a common issue for night owls trying to follow a normal working day. Our study is the first to show a potential intrinsic neuronal mechanism behind why ‘night owls’ may face cognitive disadvantages when being forced to fit into these constraints,” said Facer-Childs, who is now based at the Monash Institute for Cognitive and Clinical Neurosciences in Melbourne, Australia.
“To manage this, we need to get better at taking an individual’s personal body clock into account — particularly in the world of work. A typical day might last from 9 a.m.-5 p.m., but for a night owl, this could result in diminished performance during the morning, lower brain connectivity in regions linked to consciousness and increased daytime sleepiness.”
“If, as a society, we could be more flexible about how we manage time we could go a long way towards maximizing productivity and minimizing health risks.”
The findings are published in the journal Sleep.
Source: University of Birmingham