Discrepant Sleep or Social Jetlag
After a brief introduction by Steffi Czerny – full of personal anecdotes as always – Dr. Till Roenneberg and Esther Dyson step onto the stage at DLD13 to discuss sleep. Roenneberg is a chronobiology professor and the vice-chair of the Institute for Medical Psychology at the Ludwig-Maximilians-Universität, Munich, amongst other memberships.
Dyson is a DLD veteran known primarily for her investment in- and nurturing of start-ups. Recently she has primarily focused on aerospace and health care, making her well-equipped to moderate Roenneberg's talk.
Roenneberg has been studying circadian rhythms for over 40 years, since he was 17-years-old. "I was working mainly in the lab… Ten years ago I realised humans were really the best subject. So now I'm also outside the lab."
Over 150,000 people are already involved in Roenneberg's sleep project. The large sample has enabled Roenneberg to gain deeper insight into our sleep than ever before. "We discovered the huge discrepancy between what a person’s body clock wants and what their boss want.” He called this discrepancy social jetlag. "People are living in two time zones," he continues in his casual tone. "They are flying back and forth between the week and the weekend."
The book in which Roenneberg describes these findings is 'Internal Time' (or 'Wie Wir Ticken' in German).
Roenneberg explains that although while there may be early birds and night owls, we all share a 24-hour clock.
Dyson says she has heard of people with longer rhythms, but Roenneberg insists everyone's is 24 hours. "What about if you were to put people in a dark room for three days?" asks Dyson. "If you'd put them in dark room for 3 days all you'd get is a whole lot of trouble with the ethics committee," Roenneberg says, cracking an amused smile.
Roenneberg moves on to explain why most of us are sleep deprived. "We have photosensitive receptors cells in our eyes," which act like light detectors. These tell the brain whether it's summer or winter. When we sit inside in normal lighting conditions we are exposed to 300 lux. If we go outside, even on a cloudy winter's day such as today, that rises to 10,000 lux. On a sunny day it can be up to 100,000 lux.
Because we typically work in offices, remaining inside all day, our brain is constantly told it is winter. "And if you don't get enough light during the day, your clock moves back," Roenneberg says. That means that many people who struggle to wake early may actually be morning birds, but don't realise this because their bodies are confused. In fact, Roenneberg says most Europeans and Americans only ever have recovery sleep, because everyone has a sleep deficiency. "Which actually makes all of this sleep research bogus if you think about it, because we have no idea what normal sleep is."
Dyson clearly believes in the beneficial effects of light. She is wearing a Valkee headset (which shines light into the ears) while chatting to Roenneberg. Although he does not think such a system can truly work, he laughs easily and says: "If it works for you, that's great – that's all you need! I'm actually bored of those scientists who think they know everything..."
Roenneberg and Dyson move on to mention the correlation between lack of light exposure and depression and the fact that we should all be trying to take medicine according to our body's rhythm next.
"Everything in our body is timed,” Roenneberg explains. Even our genes switch on and off depending on the time of day. This shows that it is crucial to take medicine at the correct time. The question remains, however, what the correct time is? Roenneberg simply emphasises everyone's individuality, prompting Dyson to wonder: "So your basic advice is to pay attention to this [rhythm] but you can’t give any general advice?"
Roenneberg can only nod.
“Would you tell audience members to skip tonight’s party?” she probes further.
"Never skip a party," Roenneberg answers definitively. "Especially if you're still in a reproductive age."
Final words of the discussion are that you can never oversleep. You can overeat, but you cannot oversleep. Seems like the perfect motto to start a napping tradition.