|University of Munich
|MCTQ, Chronotype, Social Jet Lag, Aschoff Ruler
|Max Planck Institute for Behavioral Physiology, University of Munich, University College London, Harvard University
Till Roenneberg (born 4 May 1953) is a professor of chronobiology at the Institute of Medical Psychology at Ludwig-Maximilian University (LMU) in Munich, Germany. Roenneberg, in collaboration with Martha Merrow, explores the impact of light on human circadian rhythms, focusing on aspects such as chronotypes and social jet lag in relation to health benefits.
Roenneberg was born in Munich, Germany. He began working with Jürgen Aschoff at the age of 17.
Roenneberg attended both the University College London and Ludwig Maximilian University of Munich where he began by studying physics. He switched to medicine in order to focus on the science of the human body, but ended up studying biology. As a postdoctoral fellow, he studied again under Jürgen Aschoff, studying annual rhythms in the body, then moved to the United States to study the cellular basis of biological clocks under Woody Hastings at Harvard University.
In 1991, he began the tradition of giving the Aschoff's Ruler prize to a chronobiologist who has advanced the field.
He is currently the vice-chair of the Institute for Medical Psychology of the Ludwig Maximilian University of Munich, the head of the Centre for Chronobiology, the president-elect of the European Biological Rhythms Society, the president of the World Federation of Societies for Chronobiology, and a member of the Senior Common Room of Brasenose College, University of Oxford. From 2005 to 2010 he was the coordinator of "EUCLOCK" and coordinator of the Daimler-Benz-Foundation network "ClockWORK", and from 2010 to 2012 was the member at large of the Society for Research of Biological Rhythms
Aside from human chronobiology, Roenneberg has significantly contributed to other aspects of the chronobiology field. He has done extensive work on dinoflagellates, a unicellular organism, and has been able to show that even this simple organism is capable of possessing two independent rhythms, providing evidence that a single cell can have two different oscillators. In addition, his work on dinoflagellates has been able to show that these two independent oscillators differ to a significant extent in that they respond differently when treated with various light pulses. They found that the two oscillators have varying sensitivities to different types of light. The B-oscillator is most sensitive to blue light while the A oscillator is sensitive to both blue and red light.
Roenneberg has also completed work on Neurospora crassa, determining the masking qualities of entrainment through a Frequency (gene)-null circadian oscillator. He observed in the period of spore production (conidia bands) the phenomenon of masking, an unexpected effect on circadian entrainment due to a particular zeitgeber (such as lightor temperature). Masking has significant implications not only for future studies – which must attempt to demask affected data – but also in relation to entrainment in everyday life.
One of Till Roenneberg's most renowned accomplishments is the development of the Munich Chronotype Questionnaire (MCTQ). As a collaboration with Martha Merrow at LMU Munchen, the MCTQ samples sleep and circadian rhythm data from more than 25,000 participants. Unlike other chronotyping methods, which address the psychology of sleep, the MCTQ measures the phase angle of entrainment,the difference between an organism's intrinsic circadian period and the environmental light cycle. Thus, this questionnaire is the first to use a biological foundation, rather than psychology to determine the basis of sleep schedules.
Questions about work day and free day sleep schedules, work details, and lifestyle provide data to aid in the understanding of the interplay of biological clocks and social influences. Such research has led Roenneberg to his theory of social jet lag. The MCTQ categorizes each participant into one of seven chronotype groups and utilizes data on participants’ midsleep phase and sleep debt to survey what “type” of sleeper each person is, such as late sleepers, slightly late sleepers, early sleepers, and others. From these data, the MCTQ offers methods to make up for sleep debt (if any), and offers suggestions on what to do to wake up earlier or sleep later.
This chronotype questionnaire is important because it delves into the social aspects of circadian rhythms. By testing behavior rather than directly testing genetic factors, the MCTQ may offer new information regarding how the effects of external factors, including geographic location, seasons, obesity, social jet lag, or shift work,may relate to genetic predispositions of circadian rhythms.
Roenneberg released a book in March 2012 titled Internal Time: Chronotypes, Social Jet Lag, and Why You're So Tired where he explains the concepts behind circadian rhythm to the masses. One of the major points in his book is, "Early birds and night owls are born, not made."Roenneberg wanted to rid people of labels such as "lazy" that frequently get placed upon those who wake up late. With this book, he wanted to deliver his point that these sleep patterns are due to people's genetics and are not from choice. He discusses how everyone is born with an internal clock, and living a lifestyle in dissonance with this inherent biological clock puts individuals at greater risk for health problems. Roenneberg introduces the term “social jet lag," saying it is more dangerous than normal jet lag because social jet lag forces individuals to persistently go against their biological clock in a consistent light/dark cycle. In this book, he defines social jet lag as “the difference between midsleep on free days and midsleep on work days." Free days are defined as days without an alarm clock, where one naturally wakes up, and work days where one wakes up with an alarm clock. Midsleep is defined as the midpoint of an individual's sleeping period. One of the significant health risks of social jet lag is obesity, and Roenneberg claims that for every hour of social jet lag, the probability of being overweight increases by approximately 33%. In fact, social jet lag is so prevalent that Roenneberg claims that 87% of the population of Central Europe suffers from social jet lag to some degree.
Roenneberg also claims that adolescents, biologically, have an internal clock that causes their midsleep to fall later than young infants and adults. Thus, teenagers are not lazy, but are simply following their internal rhythms by going to sleep later and waking up later. This late midsleep pattern changes after adolescence, but at different points for men and women. Women's midsleep changes around age eighteen, while men's midsleep changes at the age of twenty-one. Forcing teenagers to wake up early, against their internal rhythms, leads to stress. As many studies have shown, stress leads to unhealthy decisions such as smoking and drinking.
Some of Roenneberg's publications include:
Jet lag is a physiological condition that results from alterations to the body's circadian rhythms caused by rapid long-distance trans-meridian travel. For example, someone flying from New York to London, i.e. from west to east, feels as if the time were five hours earlier than local time, and someone travelling from London to New York, i.e. from east to west, feels as if the time were five hours later than local time. The phase shift when traveling from east to west is referred to as phase-delay of the circadian circle, whereas going west to east is phase-advance of the circadian circle. Most travelers find that it is harder to timezone adjust when traveling to the east. Jet lag was previously classified as one of the circadian rhythm sleep disorders.
A circadian rhythm, or circadian cycle, is a natural oscillation that repeats roughly every 24 hours. Circadian rhythms can refer to any process that originates within an organism and responds to the environment. Circadian rhythms are regulated by a circadian clock whose primary function is to rhythmically co-ordinate biological processes so they occur at the correct time to maximise the fitness of an individual. Circadian rhythms have been widely observed in animals, plants, fungi and cyanobacteria and there is evidence that they evolved independently in each of these kingdoms of life.
Chronobiology is a field of biology that examines timing processes, including periodic (cyclic) phenomena in living organisms, such as their adaptation to solar- and lunar-related rhythms. These cycles are known as biological rhythms. Chronobiology comes from the ancient Greek χρόνος, and biology, which pertains to the study, or science, of life. The related terms chronomics and chronome have been used in some cases to describe either the molecular mechanisms involved in chronobiological phenomena or the more quantitative aspects of chronobiology, particularly where comparison of cycles between organisms is required.
The suprachiasmatic nucleus or nuclei (SCN) is a small region of the brain in the hypothalamus, situated directly above the optic chiasm. It is the principle circadian pacemaker in mammals and is necessary for generating circadian rhythms. Reception of light inputs from photosensitive retinal ganglion cells allow the SCN to coordinate the subordinate cellular clocks of the body and entrain to the environment. The neuronal and hormonal activities it generates regulate many different body functions in an approximately 24-hour cycle.
A zeitgeber is any external or environmental cue that entrains or synchronizes an organism's biological rhythms, usually naturally occurring and serving to entrain to the Earth's 24-hour light/dark and 12-month cycles.
A night owl, evening person or simply owl, is a person who tends to stay up until late at night, or to the very early hours of the morning. Night owls who are involuntarily unable to fall asleep for several hours after a normal time may have delayed sleep phase disorder.
Circadian rhythm sleep disorders (CRSD), also known as circadian rhythm sleep-wake disorders (CRSWD), are a family of sleep disorders which affect the timing of sleep. CRSDs arise from a persistent pattern of sleep/wake disturbances that can be caused either by dysfunction in one's biological clock system, or by misalignment between one's endogenous oscillator and externally imposed cues. As a result of this mismatch, those affected by circadian rhythm sleep disorders have a tendency to fall asleep at unconventional time points in the day. These occurrences often lead to recurring instances of disturbed rest, where individuals affected by the disorder are unable to go to sleep and awaken at "normal" times for work, school, and other social obligations. Delayed sleep phase disorder, advanced sleep phase disorder, non-24-hour sleep–wake disorder and irregular sleep–wake rhythm disorder represents the four main types of CRSD.
In the study of chronobiology, entrainment occurs when rhythmic physiological or behavioral events match their period to that of an environmental oscillation. It is ultimately the interaction between circadian rhythms and the environment. A central example is the entrainment of circadian rhythms to the daily light–dark cycle, which ultimately is determined by the Earth's rotation. Exposure to certain environmental stimuli will cue a phase shift, and abrupt change in the timing of the rhythm. Entrainment helps organisms maintain an adaptive phase relationship with the environment as well as prevent drifting of a free running rhythm. This stable phase relationship achieved is thought to be the main function of entrainment.
A chronotype is the behavioral manifestation of underlying circadian rhythm's myriad of physical processes. A person's chronotype is the propensity for the individual to sleep at a particular time during a 24-hour period. Eveningness and morningness are the two extremes with most individuals having some flexibility in the timing of their sleep period. However, across development there are changes in the propensity of the sleep period with pre-pubescent children preferring an advanced sleep period, adolescents preferring a delayed sleep period and many elderly preferring an advanced sleep period.
Light effects on circadian rhythm are the effects that light has on circadian rhythm.
Jürgen Walther Ludwig Aschoff was a German physician, biologist and behavioral physiologist. Together with Erwin Bünning and Colin Pittendrigh, he is considered to be a co-founder of the field of chronobiology.
A lark, early bird, morning person, or an A-person, is a person who usually gets up early in the morning and goes to bed early in the evening. The term relates to the birds known as larks, which are known to sing before dawn. Human "larks" may sleep from around 10 p.m. to 6 a.m., and tend to feel most energetic just after they get up in the morning. They are thus well-suited for working the day shift.
The Munich Chronotype Questionnaire (MCTQ) was created in 1976 by Till Roenneberg and Martha Merrow at Ludwig-Maximilians University (LMU) Munich. The MCTQ samples sleep and circadian rhythm data from more than 25,000 participants.
Hitoshi Okamura is a Japanese scientist who specializes in chronobiology. He is currently a Professor of Systems Biology at Kyoto University Graduate School of Pharmaceutical Sciences and the Research Director of the Japan Science Technology Institute, CREST. Okamura's research group cloned mammalian Period genes, visualized clock oscillation at the single cell level in the central clock of the SCN, and proposed a time-signal neuronal pathway to the adrenal gland. He received a Medal of Honor with Purple Ribbon in 2007 for his research and was awarded Aschoff's Ruler for his work on circadian rhythms in rodents. His lab recently revealed the effects of m6A mRNA methylation on the circadian clock, neuronal communications in jet lag, and the role of dysregulated clocks in salt-induced hypertension.
Martha Merrow is an American chronobiologist. She currently chairs the Institute of Medical Psychology at the Ludwig Maximilian University of Munich. Her career focuses primarily on investigating the molecular and genetic mechanisms of the circadian clock. Since joining the Ludwig Maximilian University in 1996, Merrow has investigated molecular and genetic mechanisms of the circadian clock as well as daily human behavior and medical psychology.
Jay Dunlap is an American chronobiologist and photobiologist who has made significant contributions to the field of chronobiology by investigating the underlying mechanisms of circadian systems in Neurospora, a fungus commonly used as a model organism in biology, and in mice and mammalian cell culture models. Major contributions by Jay Dunlap include his work investigating the role of frq and wc clock genes in circadian rhythmicity, and his leadership in coordinating the whole genome knockout collection for Neurospora. He is currently the Nathan Smith Professor of Molecular and Systems Biology at the Geisel School of Medicine at Dartmouth. He and his colleague Jennifer Loros have mentored numerous students and postdoctoral fellows, many of whom presently hold positions at various academic institutions.
In the field of chronobiology, the dual circadian oscillator model refers to a model of entrainment initially proposed by Colin Pittendrigh and Serge Daan. The dual oscillator model suggests the presence of two coupled circadian oscillators: E (evening) and M (morning). The E oscillator is responsible for entraining the organism’s evening activity to dusk cues when the daylight fades, while the M oscillator is responsible for entraining the organism’s morning activity to dawn cues, when daylight increases. The E and M oscillators operate in an antiphase relationship. As the timing of the sun's position fluctuates over the course of the year, the oscillators' periods adjust accordingly. Other oscillators, including seasonal oscillators, have been found to work in conjunction with circadian oscillators in order to time different behaviors in organisms such as fruit flies.
The bunker experiment was a scientific experiment that began in 1966 to test whether humans, like other species, have an intrinsic circadian clock. It was started by Jürgen Aschoff and Rütger Wever of the Max Planck Institute for Behavioral Physiology and later taken over by Jürgen Zulley. Participants lived in a bunker for multiple weeks while scientists measured their daily rhythms in many variables. The main conclusion of the experiment was that humans have an intrinsic clock with a period greater than 24 hours. The experiment also established many features of this clock and paved the way for future circadian studies.
Ken-Ichi Honma is a Japanese chronobiologist who researches the biological mechanisms underlying circadian rhythms. After graduating from Hokkaido University School of Medicine, he practiced clinical psychiatry before beginning his research. His recent research efforts are centered around photic and non-photic entrainment, the structure of circadian clocks, and the ontogeny of circadian clocks. He often collaborates with his wife, Sato Honma, in work involving the mammalian suprachiasmatic nucleus (SCN), its components, and associated topics.
In chronobiology, photoentrainment refers to the process by which an organism's biological clock, or circadian rhythm, synchronizes to daily cycles of light and dark in the environment. The mechanisms of photoentrainment differ from organism to organism. Photoentrainment plays a major role in maintaining proper timing of physiological processes and coordinating behavior within the natural environment. Studying organisms’ different photoentrainment mechanisms sheds light on how organisms may adapt to anthropogenic changes to the environment.