xxxvii. Daylight Saving Time / Summer Time

27 October 2007 at 13:33 | Posted in Circadian rhythm | Leave a comment
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In 2005, Kazakhstan stopped using Summer Time (Daylight Saving Time, DST). Dr. Zaira Majitova, MD, said: “A human body has its own biological watch which runs synchronously with nature’s watch. When the human body is forced to readjust artificially, it leads to disturbances in the biological watch.” Doctors reported a long list of health complications resulting from the hour lost in the springtime.

In 2006, Finnish researchers at their National Public Health Institute published their study showing that the transition to daylight saving time reduces sleep duration by over an hour and reduces sleep efficiency by an average of 10%.

Now in 2007, scientists in Germany and Switzerland report: The Human Circadian Clock’s Seasonal Adjustment Is Disrupted by Daylight Saving Time. Two studies are here rolled into one.  First, data from a large survey which examined sleep patterns of 55 000 people in Central Europe were mined. Under standard time, sleep timing on free — usually weekend — days follows the seasonal progression of dawn. Under summer time, it does not.

In the second study, they analyzed the timing of sleep and activity for eight weeks around each of the two annual transitions in 50 people, taking into account each individual’s natural chronotype, ranging from morning larks to night owls. They found that the timing of both sleep and peak activity levels readily adjust to the release from DST in autumn, but that the timing of activity does not adjust to the start of DST in spring. In everyone, but especially in the night owl chronotypes, biological timing stays on standard (winter) time, while our social schedules must be adjusted to the advanced clock time throughout the summer. “When we implement small changes into a biological system which by themselves seem trivial, their effects, when viewed in a broader context, may have a much larger impact than we had thought,” says Till Roenneberg of Ludwig-Maximilian-University in Munich.

Both sleep times and daily activity patterns were tracked. The time of mid-sleep in the large population correlates with dawn under standard time but is widely scattered under DST. In the smaller study, daily activity patterns most clearly show the lack of adjustment to DST; sleep times show the same thing but to a lesser degree.

From the study report: “the human circadian clock tracks dawn under standard time but not under DST. Whereas the human clock … predictably advances from autumn to spring …, it remains locked to the same time between spring and autumn…. These results, in combination with those from the database, suggest that the incomplete adjustment of activity in larks and the nonadjustment in owls continues … throughout the months of DST.”

“Like other animals, humans are seasonal (in birth rates, mortality, suicide rates, etc.). However, seasonality in humans has drastically declined in industrialized countries over the last 60 years. The main reason for this is probably increased shielding from [nature], but DST might constitute an additional factor for the dissociation of human biology from the seasons.” I do so agree. Our circadian rhythms are primarily connected to dawn, not to sundown. A Wikipedia illustration shows very clearly how our exposure to the natural dawn cycle is changed by our use of daylight “saving” time.

Figure 4, “Relationship between Natural and Behavioral Light-Dark Cycles with and without DST” in the 2007 report linked to above, shows and explains the same thing. There, the “enforced delay of seasonal progression” is shown, and it’s pointed out that the “amplitude of the relationships as well as the degree of their perturbations by DST increase with latitude.”

A quarter of the world’s population is subjected to the one-hour time change twice a year, and the impact is still not understood. I’ve never liked DST, but I’ll let Coturnix say it for me: “In this day and age of around-the-clock life, global communications, telecommuting, etc., the clock-shifting twice a year has outlived its usefulness and should go the way of the dodo.”

I’m writing this blog post at exactly the wrong time of year, of course. All studies show that in the autumn, everyone fully adjusts to standard time within a week. It’s the transition in spring which causes problems.


Next:  xxxviii. Eveningness vs. DSPS



xxxiii. Owls of the World, Unite!

24 March 2007 at 12:57 | Posted in Circadian rhythm | 2 Comments
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In Denmark, Norway and possibly other countries ‘larks’ (early-risers) are called ‘A-people’ while ‘owls’ (late-risers) are ‘B-people’. Language is important in defining issues, so this terminology is unfortunate, I think, but it is well-established. Just the fact that there is a defining terminology in various languages is an admission that there is an issue. The common terms in English, larks for morningness and owls for eveningness, seem much less (de-)grading. 

 Danes are, in my experience, good organizers. In late December 2006, the B-Society, ‘B-samfundet’, went public and it now has nearly 4000 members and a newsletter in Danish. On its web page, its goals are defined in Danish and in English. [Update, June 2007: There’s now an international site in English: The B-Society.] There is a page for comments [now defunct, replaced by forum], which are appearing thick and fast in the Scandinavian languages as well as English and others; spam is also appearing, so something needs to be done about that.

The B-Society wants the world to please forget the archaic requirement for all work to be done while the sun is up and preferably just as soon as it’s up. When everyone must appear at work and school at the same time in the (early) morning, traffic jams result and up to half of the workers will not be performing at peak capacity for several hours yet. We’ve had electric light for well over a century, and it is past time to make some changes to everyone’s benefit.   

To quote the site (I’ve corrected their halting English some): “… it is unproductive for ‘owls’ dealing with knowledge, creativity and innovation to be at work at 8:00 a.m. without being present mentally, since their productivity peaks in the afternoon and in the evening. The different rhythms of people will generate a good bottom line in the innovation-driven society.”

One concrete project which may show some promise is awarding “certification” to employers who are friendly to “owls”, aka B-people. As they put it: “The B-Society is working with B-Certification of employers who accept and respect the working rhythm of ‘owls’. B-Certification will enable ‘owls’ to navigate in the labour market and find those workplaces that actually implement flexible working hours as well as show respect for and acceptance of the life and work rhythm of ‘owls’.
Now this is an idea whose time has come! The B-Society seems not to have heard of Delayed Sleep-Wake Syndrome (DSPS), only the eveningness of fairly normal “owls”. Yet achievement of their goals will obviously help us, too, as sleep deprivation is nasty for all of us. More power to them!
The chronobiologist “Coturnix” has a blog entry about the B-Society here. I borrowed his title.
And the remarkable photo of an attacking owl is the winner of National Wildlife’s 35th annual photography competition. Kim Steininger of Pennsylvania took the picture in Ontario, Canada, last winter. She noticed that one of the great gray owls was staring back at her. “I didn’t think anything of it until it started flying at me,” she says. Before getting out of the way, she captured this digital photo with a 500mm telephoto lens.



Next:  xxxiv. Guest Blogger: Alan West


xviii. [CHAPTER TWO] Phase Response Curve

4 December 2005 at 14:59 | Posted in Circadian rhythm | 7 Comments
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“Chapter” One ended, appropriately I think, with a break.  A coffee break…  On to Chapter Two! 
A half a year ago, I was struggling to understand what a Phase Response Curve (PRC) is.  Now I’ve drawn one and am going to try to explain it.  In the illustration you can see, obviously, the 24 hours of a day / night on the horizontal, and a good night’s sleep for the person whose PRC is shown.  It’s not mine, not yours, but someone’s Phase Response Curve, similar for all humans.  (Source )  (Another example
The hours are clock hours, only if this person’s circadian period happens to be exactly 24 clock hours long.  Most people have a period a bit longer than 24 hours, and will need to advance the phase, shift it earlier, each day. 
The human PRC for light
This curve shows what light administration does for the timing of the Core Body Temperature in humans.  In general, several other circadian rhythms follow the body temperature rhythm. 
The numbers on the vertical axis represent hours of phase shift.  Very bright light to the eyes of this person, immediately upon awakening, will shift her phase two hours earlier, a two-hour advance.  Just a few hours later, light won’t have any effect (in the “dead zone”, where the curve follows the zero-line).  Toward bedtime, exposure to light has the opposite effect; the negative numbers represent a phase delay.  Very bright light just before bedtime will cause a two-hour delay, cancelling out the morning’s advance.  However, the light we usually are exposed to in the evening hours will be considerably less intense.  
While the “dead zone” in midday can last for several hours, the “dead zone” in our subjective night lasts for only a moment.  Light exposure shortly thereafter, on the rising portion of the curve, can create a mess according to this chronobiologist.  Exposure to light too many minutes before our spontaneous wake-up time is thus an uncertain business. 
Those of us with Delayed Sleep-Phase Syndrome probably have a circadian period which is longer than normal.  We need to phase advance quite a bit each day, just to adjust to nature’s 24 hours.  Advancing even more, in order to awaken at a “normal” time, is impossible without treatment such as that described in my entry no. xvi. 
 Have I misunderstood something?  Corrections are welcome! 
Next post:  xix. Phase Response Curve (2) 


xv. Why don’t doctors know?

28 November 2005 at 16:37 | Posted in Circadian rhythm | 11 Comments
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Not many doctors know anything about circadian rhythms.  Not even those calling themselves “sleep specialists” at “sleep clinics”.  Why? 
Well, the history of the field doesn’t go far back.  Some observations were made in the 1700s (the plant in the dark cupboard; Linne’s flower clock), 1800s (experiments and observations, again mostly on plants) and pre-WWII (humans in dark caves; photoperiodism – short and long day plants). 
Research and knowledge exploded in the last half of the 1900s.  In all directions, as explosions are wont to do.  Medicine studied brain waves and sleep stages in humans.  Biology, the mechanisms of seasonal migration and daily activity.  The terms “circadian rhythms” and “biological clock” weren’t even coined until less than a half a century ago.  There’s been constant work on all levels, evolutionary to molecular to wondering why organisms need to sleep at all.  Nature and nurture on all levels. 
No one can keep up with the details of all this as it is happening.  And no one is steering — setting priorities — except perhaps those who provide funding for research.  Someone has to choose what is sufficiently well documented and what is important enough for medical students to study. 
Apnea is widespread, dramatic (it kills) and treatable.  Fine.  Students learn about apnea.  Journalists pick up on and tell people about narcolepsy with cataplexy — both the words and the effects appeal; they sell newspapers.  Pills are provided for insomnia.  Sleep medicine is thus covered — on to the next item. 
Circadian rhythm disorders are “new”.  Discovered, defined and accepted by the 90s or so.  Many doctors now in practice were educated earlier than that and must be forgiven. 
The experts ’til now have been the psychiatrists and the neurologists.  Strange bedfellows, it seems to me, but that may just reveal how little I know about those fields.  In the USA, sleep medicine has now been approved as a sub-specialty for physicians practicing psychiatry, neurology, internal medicine and pediatrics. 
Requirements for the one year program include Chronobiological mechanismsCircadian rhythm disorders is mentioned under Treatment strategies.  The approval came in March 2005, and institutions wishing to offer the program were invited to apply for accreditation.  So no candidates can have completed the program to date.  That’s how new the field is!


Next post:  xvi. Treatment


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