9.General mortality does not specify the cause of death. The death of elderly people strongly contributes to the general mortality rates, and the causes of their deaths include cancer, fatal cardiovascular incidents, or simply old age (which could mean any undetermined reason for dying).
10.It surely is only a coincidence that Christians celebrate the birth of Jesus nine months after the conception peak in the Holy Land.
11.In this latitudinal gradient, human reproduction rhythms resemble the wave of cherry blossoms that occur first in the south of Europe and progressively later toward the north.
12.For example, conception might have been planned so that the months around birth interfere least with the peak of workload on the farm.
13.Only about 60 percent of conceptions actually lead to a birth. The number of natural abortions of unrecognized pregnancies during their first weeks might even decrease this rate.
14.We are still waiting for an experiment to be performed with the hypothesis that we are more immune to microbial attacks if we live strictly by photoperiod, but we do know that the immune system changes with season.
23. Professional Selection
1.With the peer review process, science ensures that scientific publications are of high quality: that the experiments use adequate methods and protocols; that the results are believable; and that the authors’ interpretations make sense. Researchers submit their manuscript to the editor of a journal, who looks at the title, the keywords, and the short abstract, which always accompany a scientific paper, and then decides to whom she will send the manuscript for review. Usually, three reviewers are chosen who are experts in the scientific field to which the content of the paper belongs. The reviewers are often colleagues or even competitors of the authors who work at other institutions. If they do their job properly, they read the entire paper and then write a review that contains constructive criticism, makes suggestions on content and style, and even, in some rare cases, demands additional experiments to substantiate the authors’ case. These comments are sent back to the editor, who sends them to the authors. The identities of the reviewers are usually kept anonymous. Depending on the quality of the manuscript and the reviews, a paper can be accepted as is, accepted with some minor or major revisions, or even rejected.
2.Interns work very hard in long shifts for days on end during their first years in the clinic after finishing medical school. The unhealthy working hours of young doctors are a problem worldwide, but they are especially grueling in the United States.
3.See S. W. Lockley, J. W. Cronin, E. E. Evans, B. E. Cade, C. J. Lee, C. P. Landrigan, J. M. Rothschild, J. T. Katz, C. M. Lilly, P. H. Stone, D. Aeschbach, and C. A. Czeisler (2004). Effect of reducing interns’ weekly work hours on sleep and attentional failures. New England Journal of Medicine 351(18):1829. The principal investigator was Charles A. Czeisler. The intervention schedule eliminated extended work shifts (those greater than twenty-four hours) and reduced the number of hours worked per week. A medical error was defined as that which causes harm or has substantial potential to cause harm, including preventable adverse events, unintercepted serious errors, and intercepted serious errors. Not included were errors with little or no potential for harm or unpreventable adverse events.
4.Oscar, the fictional transplant surgeon from a previous chapter, was a definite early type.
5.As in all statistical and global assessments, there are surely many exceptions. But I would argue that extreme late chronotypes are rare among teachers—they would be as easy a prey to the students as Ann was to her brother Toby in the first chapter. Any late-chronotype teacher must be especially dedicated to muster the strength to teach every school morning.
6.The baseline period equaled two weeks before the subjects were infected with the rhinovirus. The researchers could also rule out other potential confounders, like demographics, season of the year, body mass, socioeconomic status, psychological variables, or health practices.
7.I am not, of course, implying that late types are handicapped, except for their difficulties in complying with social times.
8.This slogan has recently been picked up by a chain of coffee shops.
9.This mutation occurs in the human DEC2 gene, the product of which suppresses the transcription of other genes. See Y. He, C. R. Jones, N. Fujiki, Y. Xu, B. Guo, J. L. Holder Jr., M. J. Rossner, S. Nishino, and Y-H. Fu (2009). The transcriptional repressor DEC2 regulates sleep length in mammals. Science (14 August):866–870.
10.Patients suffering from Smith-Magenis syndrome have a deletion of a large region on their chromosome 17, which normally carries the genetic information of many genes. Due to this deletion, many important proteins cannot be produced.
11.Beta-blockers are drugs used in cardiac arrhythmias, treatment after a heart attack, or in hypertension. They block the activation of certain synapses and can also block the production of melatonin.
12.Questionnaires assessing time-of-day preferences ask people what they would like to do according to their “feeling-best rhythm”: when they would sleep, schedule important work, or exercise. Depending on the answers, every item is given a certain number of points. The resulting sum (score or “morningness-eveningness” scale) then determines whether someone is a morning or an evening type. Although time-of-day preferences loosely correlate with chronotype, they do not readily measure the body clock’s phase of entrainment (chronotype). The questionnaire for these personality traits is called the Big Five Inventory, and its questions can be found on the internet. To give you an idea of the sort of statements subjects have to respond to, here is a sample of those used in the category “neuroticism”: I am easily disturbed; I change my mood a lot; I get irritated easily; I get stressed out easily; I get upset easily; I have frequent mood swings; I worry about things; I am relaxed most of the time.
13.It would be interesting to know the chronotype of the authors of these studies—I wonder if they belong to the late types and therefore think poorly of early types.
14.Hippocrates was a physician in ancient Greece (460–370 B.C.), the inventor of the Hippocratic Oath, which is still the basis of modern doctors’ professional ethics. The body fluids on which he based his theory were blood, phlegm, black bile, and yellow bile, all of which he related to the four “humors”: sanguine, phlegmatic, choleric, and melancholic.
15.Ernst Kretschmer (1888–1964) was a German psychiatrist at the University of Marburg. The body types underlying his typology were: asthenic/leptosomic (thin, small, weak); athletic (muscular, with large bones and strong); and pyknic (stocky, fat).
16.Hans Jürgen Eysenck (1916–1997) was born in Berlin but moved to England (University College, London) because he openly opposed the Nazis. He used factor analysis to find clusters of different personality traits that appeared to go together in individuals. He concluded that there are only two major personality traits: neuroticism (people who tend to experience negative emotions) and extraversion (people who tend to enjoy positive events, especially in social contexts). Eysenck concluded that a graded mixture of these two traits can describe all personalities.
17.When comparing the results of the MCTQ with those of the morningness-eveningness (ME) questionnaire, the best correlation was found between the ME score and the single question: What chronotype do you think you are if you had to choose from seven categories, ranging from extreme early to extreme late? We have already discussed how little these answers correlate with the chronotype determined by midsleep on free days and how much these subjective assessments depended on the preferences of other people, such as partners.
24. The Nocturnal Bottleneck
1.Researchers once performed a fascinating experiment with basketball players. They had the players aim carefully at the hoop and trained them to throw the ball once they heard a sound signal. Half the time, the lights went out when the signal sounded, and the other half, the lights stayed on. They then counted the success rate of the throws and found that the basketball players were significantly
more successful in the dark than in the light. I wonder whether professional basketball players close their eyes when they initiate their throw.
2.The lovely German word Zeitraum (time-space) helps to distinguish between the flow of time, such as the passing of an hour, and a temporal structure, such as tides, days, months, and years.
3.“Ebo” was the successor of Jürgen Aschoff at the Max Planck Institute in Andechs. Unfortunately, he died much too young. See E. Gwinner (1996). Circadian and circannual programmes in avian migration. Journal of Experimental Biology 199:39–48.
4.The Austrian biologist Karl von Frisch (1886–1982) had conducted similar experiments with honey bees. When they discover a pollen source, honey bees return to the hive and report the direction and the distance of the food source to their hive mates by performing a waggle dance. They could only report the location of the food source accurately by using their body clock. Karl von Frisch received the Nobel Prize in 1973, together with Niko Tinbergen and Konrad Lorenz—all pioneers of the new field of ethology (physiology of behavior).
5.The internal representation of the Zeitraum day and that of space are constantly working as a team; most of the things that are best done at a certain time of day or night also have spatial qualities. This has been extensively investigated in experiments that involve placing food at different locations (for example, in a maze) at specific times. Animals learn these time-place tasks with ease.
6.Organisms have occupied the most exotic niches, for example volcanic vents at the bottom of the ocean where the surrounding water is extremely hot and almost saturated with sulfur. Some bacteria specialize their metabolism to cope with these harsh conditions. According to the rules of evolution these adaptations are never directed; an organism cannot alter its genome “with the aim” of occupying a niche. Adaptation to a new niche happens extremely gradually through combinations of chance mutations and natural selection.
7.These cells with a nucleus are called eukaryotes (as opposed to bacteria, which are prokaryotes and have no nucleus in their cell). The nucleus is a dedicated cellular compartment that contains the DNA coiled up in chromosomes.
8.Land was conquered by insects much earlier; of course, plants had done so long before.
9.Life under water was much more buffered against temperature changes than life on land. Amphibians, which breathe air and can walk on dry land, can always go back into the water if the night gets too cold or the day too hot. But reptiles had to make a choice—either adapt to the cold nights or adapt to the warm days.
10.The first mammals were probably all very small, hairy insect eaters (insectivores).
Acknowledgments
Many friendly and benevolently critical people have participated in the development of this book, continuously helping me look at it with reader’s rather than writer’s eyes. Family, friends, even neighbors have read chapters as soon as I thought them presentable, always coming back with gentle hints for improvements. Carlos Mamblona diligently pointed out inconsistencies. I am indebted to my friends and colleagues Woody Hastings, Therese Wilson, and Mike Menaker for many valuable suggestions. Anna Wirz-Justice was often and in many different locations a critical listener. My wife, Iris, was instrumental in helping me with the plots of the stories and in bringing their characters to life. But above all, Harry Lubasz and Alison Abbot were my loyal warrantors for correctness, plausibility, and language. The writing of this book would have been half as much fun without all these lovely people!
Index
Actimeters, 98, 104, 177, 180, 247n2, 254n6
Activity–rest cycle, 24–30, 36–46, 58, 86, 96–105, 180–183, 238n1. See also Sleep–wake cycle
Adolescence: vs. puberty, 101–102, 248n4; and chronotype, 101–104, 109, 110–113, 161–162, 196, 251n6. See also Teenagers
Advanced Sleep Phase Syndrome, 68–69
Age, 10, 11; relationship to sleep, 95, 96–105, 247n1; relationship to chronotype, 95, 99–105, 109, 151, 161–162, 191, 193–201, 217, 230, 251n6; and hormones, 102. See also Adolescence; Elderly, the; Teenagers
Agriculture, 205, 209, 230
Alarm clocks, 47, 138, 142, 143, 146–147, 164, 251n1
Algae, 5, 81–89, 231, 246n5, 250n6
Amino acids, 241n3, 243n2, 244n4
Amphibians, 57, 58, 262n9
Andechs bunker experiments, 238n4; sleep–wake cycle in, 36–46, 52–53, 54, 86, 94; and Aschoff, 40–41, 43–45, 48–49, 239n1; and Wever, 41, 48–49, 239n1; and internal desynchronization, 43–45, 86, 133; metabolites collected in, 80
Aschoff, Jürgen, 3, 4, 205, 261n3; and Andechs bunker experiments, 40–41, 43–45, 48–49, 239n1; internal desyn-chronization hypothesis, 43–45
Baba Bulley Shah, 18, 237n1
Bell-shaped distributions, 13, 236n9
Benzer, Seymour, 63, 241n2
Beta-blockers, 220, 259n11
Big Five Inventory, 259n12
Bioluminescence, 81–84, 87–88, 246n2, 250n6
Birds, 58, 228, 229; migration of, 226–227
Birth control pill, 212
Birth rates, 208–212
Blood pressure, 68, 78, 104
Body temperature: circadian rhythm of, 14, 39–40, 42, 43–44, 78, 86, 93–94, 104, 238n1, 245n4; relationship to sleep, 39–40, 42, 43–44, 86, 93–94; yawning and brain temperature, 247n4
Borbely, Alex, 26–29
Brain, the, 223–225, 226, 240nn9,12
Bread mold, 64, 242n4
Breakfasts, 8–10, 173–174
Business Process Outsourcing (BPO) industry, 187–188
Cancer, 186–187, 188–189, 190, 255nn3,4
Carskadon, Mary, 111–112
Central Europe: chronotypes in, 13, 21, 199; social jet lag in, 149; vs. India, 155–156, 199, 255n3; time spent outdoors in, 171; DST in, 173–183. See also Germany
Children, 101–102
China, 160–161, 252n9
Chromosomes, 241n3, 242n7, 261n7
Chronobiology, 4–7, 26, 115–116, 127–128, 225
Chronopharmacology, 79
Chronotype: negative attitudes regarding late birds, 5, 16, 17, 21, 22–23; vs. sleep duration, 12, 14, 21–23, 141–147; questionnaires regarding, 12, 91–92, 100–101, 104, 143, 155–157, 170–171, 178, 196, 199, 221–222, 235n6, 247n1, 253n3, 260n17; defined, 12–14; early vs. late, 12–14, 15, 22, 66–68, 73–74, 95, 101–102, 103–105, 112–113, 122, 123–125, 127–128, 132–133, 135, 136, 138, 142–148, 161–162, 164–167, 169–170, 171–172, 179–181, 183, 190–191, 196–198, 215–219, 220–222, 230, 231, 235n1, 237n6, 250n4, 258n5, 259n13; distribution of, 12–14, 15, 110–111, 132; relationship to midsleep on free days (MSF), 12–14, 157–158, 196–197, 199, 255n2, 260n17; positive attitudes regarding early birds, 15, 16, 17–19, 21; and drugs, 79; and cortisol, 79, 104; relationship to age, 95, 99–105, 109, 151, 161–162, 191, 193–201, 217, 230, 251n6; relationship to gender, 101–102, 196–200; relationship to use of waking-up aids (WUAs), 146–147, 164, 251n1; relationship to population density, 169–170; relationship to time spent outdoors, 169–171; and DST, 177, 179–181, 183; and shift work, 190–192; self and partner assessment of, 195–200, 255nn1,2,4, 260n17; relationship to personality, 215, 219–222, 259n12; relationship to careers, 215–217, 218, 222, 230–231; vs. morningness–eveningness preferences, 221–222, 260n17. See also Sleep; Sleep–wake cycle
Circadian rhythms: in single-cell organisms, 1, 2–3, 5, 80, 81–89, 231, 242n4; defined, 43; and the liver, 74, 75–78, 79–80, 137; temperature rhythm, 78, 94; and age, 98–100; Constant Routine experiments regarding, 103–105, 136; and melatonin, 188–190; masking of, 240n6; and evolution, 242n4. See also Activity–rest cycle; Body temperature; Cognitive functions; Entrainment; Hormones; Sleep–wake cycle; Synchronization of body clocks
Cognitive functions: and body clock, 10, 11, 14, 24–25, 78, 103, 105, 106–113, 136, 151, 171, 218, 230, 250n4; and school hours, 105, 106–113, 218, 230; and jet lag, 136
Conception patterns, 208–212, 257nn
10–12
Constant Routine experiments, 103–105, 136
Cortisol, 79, 104
Cross-sectional studies, 201
Cyanobacteria, 246n8
Czeisler, Charles A., 92–94
Daan, Serge, 26–29, 236n1
Darwin, Charles, 35
Dawn, 19, 20, 253n1
Daylight saving time (DST), 160, 161, 173–183, 203, 231, 253n4, 254nn7–8
Denmark, 113, 186–187, 248n6
Depression, 206–207, 253n6, 257n7
Descartes, René, 240n9
Dinner time, 161, 162
Disco hypothesis, 102–103, 111, 161–162, 218, 251n6
Discovery of biological clock, 30
Divorce, 200–201
DNA, 72, 88, 239n5, 241n3, 244n4, 250n6, 255n2, 261n7
DNA damage, 188–190
Doctors, 214–216
Drosophila melanogaster. See Fruit flies
DST. See Daylight saving time
Dusk, 20–21
Early birds: vs. late birds, 12–14, 15, 66–68, 73–74, 101; positive attitudes regarding, 15, 16, 17–19, 21; vs. long sleepers, 21–23, 237n7. See also Chronotype
Eating habits, 10, 15, 137, 245n5, 252n12, 256n5
Edison, Thomas, 218
Education, 216–217, 258n5; school hours, 105, 106–113, 151, 218, 230
Einstein, Albert, 219, 225
Elderly, the, 98–99, 102, 247n1
Electroencephalography (EEG), 248n3, 254n6
Electrolytes, 238n1
Electrophoresis, 76–77
Entrainment, 113, 137, 148–149, 155–160, 259n12; principles of, 116, 117–128, 135, 166–167; range of, 125–127, 135, 249n4. See also Synchronization of body clocks
Enzymes, 241n3, 250n6
Epidemiology, 13, 186, 188, 189, 190, 217, 236n7
Epigenetics, 252n1
Equinox, 179, 182, 208, 209, 254n5
Ethology, 92, 247n3, 261n4
Eukaryotes, 261n7
Evolution: of biological clocks, 1, 18, 20, 45–46, 117, 212–213, 227–230, 231, 239n5, 242n4; of mammals, 228, 229, 230, 262n10; natural selection, 261n6
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