The Human Sleep Project to Establish the True Role of Sleep, Researchers Must Gather Real-World Data from Thousands, Even Millions, of People, Says Till Roenneberg

COMMENT ECOLOGY Bigger studies needed HISTORY The man behind the FICTION Ex-director of OBITUARY Joe Farman, to understand impact of bull’s-eye lens, secret of the Royal Institution discoverer of the ozone acidifying oceans p.429 modern lighthouse p.430 turns novelist p.432 hole, remembered p.435 ILLUSTRATION BY PETE ELLIS/DRAWGOOD.COM PETE BY ILLUSTRATION

The human sleep project To establish the true role of sleep, researchers must gather real-world data from thousands, even millions, of people, says Till Roenneberg.

leep is essential for health, performance list of the US National Institutes of Health One reason for this lack of understanding and wellbeing. Yet in many countries, — below, for instance, studies of tobacco is that most of what is known about sleep people are getting one to two hours (see go.nature.com/ces1rf). comes from laboratory studies. Subjects in Sless of it each night than their ancestors did Researchers have made great advances these studies tend to be mice or hamsters 50–100 years ago. Even when people have in understanding which neurotransmitters that are kept in artificial light–dark cycles, the opportunity to sleep, many cannot. Sleep and brain regions are involved in sleep2, and or people who have been instructed to sleep pathologies are approaching epidemic lev- how the timings of sleep and wakefulness are at certain times in beds that are not their els, affecting an estimated 70 million people controlled by an internal (circadian) clock3, own, with electrodes fastened to their heads. in the United States alone (see go.nature. among other things. Yet we still do not have Assessments of sleep are also often based com/6dgqhg). And in some countries, direct answers to the most basic questions. It is not on subjective responses to questions about and indirect costs of sleep-related prob- really understood, for instance, what sleep how ‘well’ people feel after they have slept, lems are thought to approach 1% of gross is for, how much is optimal, how sleep qual- or whether they think they experienced a domestic product1. Despite these alarming ity can be measured and predicted, or the good night’s sleep. To learn about sleep in the numbers, sleep research ranks only 91st in role of genetic and environmental factors in real world, and to establish how to manage the 235 categories on this year’s funding determining ideal sleeping patterns. sleep to improve productivity, health and

quality of life, we need a multidisciplinary states of modernization (people living ‘human sleep project’. LOSING SLEEP without electricity and people living in large An attempt to probe sleep in situ has been Answers to a questionnaire indicate that many cities), as well as, for instance, shift-workers, people oversleep on free days and undersleep made by my research group at the Ludwig on work days, experiencing ‘social jet lag’. people who are blind, people with metabolic 4 SOURCE: REF. Maximilian University of Munich in Ger- 10.0 syndromes, and so on. many. Since 2000, our group has been build- Together with colleagues from the chrono- 9.5 ing a database on daily sleep behaviour called Free days biology laboratory at the university hospital in the Munich Chronotype Questionnaire 9.0 Porto Alegre, Brazil, we have begun to meas- (MCTQ). We have publicized our project in ure sleep, activity, light exposure and other newspapers, on the radio and on television, 8.5 variables in an Afro-Brazilian community, the requesting people to fill out an online ques- Quilombos. This group of people is culturally 8.0 tionnaire. Participants are asked to provide and genetically homogeneous. But the diver- the times at which they go to bed, prepare 7.5 sity of the lifestyles of individual populations, for sleep, fall asleep, wake up and get up4. In which are scattered throughout Brazil, offers Sleep duration (hours) 7.0 exchange, they receive a document reveal- Work days an opportunity to investigate the changes to ing how their sleeping behaviour compares 6.5 human sleep over the past 150 years of indus- with the rest of the population. Importantly, trialization: some live on farms with no elec- 0 people give this information for both work- 0 10 20 30 40 50 60 70 80 tricity; others live and work in modern cities. ing and non-working days. Our database Age (years) A human sleep project would need around now includes entries from more than 150,000 US$30 million of funding from governments individuals from all over the world. and national and international granting Using these data, we have assessed how the This would involve inviting millions of agencies. Biotechnology companies may also amount of sleep that people get, and when people to fill out online questionnaires, tens want to invest in return for using the project’s they get it, changes with factors such as age, of thousands to keep online sleep diaries and results to guide the mass production of simple season, location and even daylight saving several thousand to submit real-time data sleep-tracking devices. Such devices will be time4. Our results suggest that although from recording devices. A subset of these valuable to sleep researchers, to physicians people sleep for the same amount of time on people would then be asked to supply their who want to diagnose and treat sleep prob- work-free days as they did ten years ago, on DNA. (Once the sleep phenotype is better lems, and perhaps even to pilots or business work days, they sleep for about 38 minutes understood, researchers would be in a good executives who want to optimize their sleep less than they used to4. We also discovered position to probe its genetics.) patterns while travelling, as well as to people that throughout their school and work- A key goal of a human sleep project would who simply want to sleep better. ing lives, people seem to oscillate between be to identify simple, effective indicators that The project could also lead people to undersleeping on work days and oversleep- sidestep the need for cumbersome electrodes, adopt more individualized schedules, which ing on work-free days (see ‘Losing sleep’), or for blood or saliva samples, which are used some fear would disrupt the synchroniza- with 80% of people needing an alarm clock to obtain conventional markers of circadian tion of societies. But if work schedules were to wake up on work days4. These findings rhythms, such as the hormone melatonin. adapted to suit the biological clocks of most indicate that much of the working population Many sleep-tracking devices are now availa- of the population, the benefits to society experiences what we call ‘social jet lag’: people ble or are in development, such as wristwatch- would outweigh a relatively small disrup- switch between different ‘time zones’ every like gadgets that measure movement and tion. The MCTQ indicates that in 44% of the week, one dictated by their work schedules, light. Other devices use information detected population assessed, the circadian timing of the other by their biological clock. by mobile phones, or communicate with people differs by only 30 minutes, and that mobile phones, which can upload data to the in 77% of the population, the timing falls BEDTIME STORY Internet. These can monitor skin temperature within a three-hour range. The practice of going to sleep and waking up and skin conductance (a measure of perspi- I am convinced that a human sleep project, at ‘unnatural’ times could be the most preva- ration, indicative of stress levels), respiration and the changes in behaviour it would bring, lent high-risk behaviour in modern society. rate, blood-oxygen levels, electrical activity could be one of the most cost-effective ways With every hour of social jet lag (the differ- in the heart, and even blood pressure. Such to improve health, performance and qual- ence between the social and the biological parameters could potentially enable research- ity of life for millions for people. A prepara- time zone), the chances of being overweight ers to establish individuals’ circadian timing, tory meeting will take place this August in or obese increase by 33% (ref. 4). This sub- and when and how well they sleep. Munich, in conjunction with the congress of stantiates an association between sleep dura- Computer scientists with expertise in the European Biological Rhythms Society. ■ tion and metabolic problems that was found biomedical, Internet and mobile-phone five years ago5. My colleagues and I have technologies will be crucial for designing Till Roenneberg is professor of also associated social jet lag with smoking, and building tracking devices, and for devel- chronobiology at the Ludwig Maximilian with increased consumption of alcohol or oping standard operating procedures for the University in Munich, Germany. caffeine4, and with signs of depression such generation, uploading and storage of data. e-mail: [email protected] as appetite loss and feelings of sadness6. Ultimately, the analysis of data collected in 1. Hillman, D. R., Murphy, A. S., Antic, R. & Pezzullo, I believe that what has emerged from such a project could give rise to fresh hypoth- L. Sleep 29, 299–305 (2006). the MCTQ database is only the tip of the eses that lead to new experiments in the labo- 2. Saper, C. B., Fuller, P. M., Pedersen, N. P., Lu, J. & iceberg. Thanks to the Internet and personal ratory. These in turn may help researchers to Scammell, T. E. Neuron 68, 1023–1042 (2010). 3. Wyatt, J. K., Ritz-De Cecco, A., Czeisler, C. A. & Dijk, monitoring devices, it should be possible to improve in situ recording methods. D.-J. Am. J. Physiol. 277, R1152–R1163 (1999). obtain systematic and quantitative informa- Data should be collected from various time 4. Roenneberg, T., Allebrandt, K. V., Merrow, M. & tion about the sleeping patterns of thousands, zones and geographical locations, and at dif- Vetter, C. Curr. Biol. 22, 939–943 (2012). 5. Van Cauter, E., Spiegel, K., Tasali, E. & Leproult, R. even millions, of people. ferent times of year. It is also important that Sleep Med. 9, S23–S28 (2008). To transform our understanding of sleep, participants represent diverse populations, 6. Levandovski, R. et al. Chronobiol. Int. 28, 771–778 a broad data-collection strategy is required. and should include people living in different (2011).