SLEEP AND RAILROADING

SLEEP AND RAILROADING

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> > There is another factor here too!  The human biological clock seems to 
> > have a "low point" someplace around 3am in the morning.  Whether or not 
> > you have enough sleep, when you hit this low point, you tend to doze 
> > off.

> I believe that this "low point" varies from person to person.  I have
> also heard that the human biological clock tends to operate on something like
> a 25-hour day, so our ability to change shifts is tied to changing in the
> direction of the natural shift of our bodies.

This is a topic for at least a 2-3 hour talk ... so here's a very brief capsule summary.

Everyone has a circadian clock of incredible accuracy. Properly timed, and with appropriate, consistent sleep (so-called "good sleep hygiene"), one can wake up 3-5 minutes before one's alarm on a daily basis. (For the doubting Thomases out there, I know this from personal experience, but have not been able to recreate the conditions since kids and med school ...)

The circadian clock is reset by bright light. Ambient room light is insufficient to do this and tends only to worsen the problem in the evenings. Sunlight is what is needed. In the absence of sunlight (studies on grad students in caves ...), one drifts over time to a 25-26 hour cycle, though some have gone into "chaotic" cycles of 18 hours and 36 hours alternating. Without adequate sun (Clevaland, Britain), people tend to be depressed (lower circulating levels of norepinephrine). More sun (So. California), and people are happy. The cycle changes with age, both in overall duration, and in timing relative to the inflexible 24-hr clock. E.g., teenagers are sleepy in the morning mostly because they are "wired" to be that way.

Humans are tropical animals. We are way out of our clime. All, or nearly all other tropical animals take a siesta. This explains our "early afternoon dip" phenomenon, which, like the tide, is biphasic: early afternoon, and wee hours after midnight. Siestas are good. As the saying goes, "[only] Mad dogs and Englishmen go out in the midday sun." This arose in India, I believe. The English, of course, did not have the necessary climatic inducements of southern Europe to see the need for a midday break, even if they had the (unrecognized) biologic ones.

Then there is the problem of shift work. Ideally, one would work the same shift all the time. However, those who work night shift never really adjust perfectly, and there is the perpetual problem of one's circadian rhythm being thrown out of whack by the sun on the morning commute home. Most people do not want the same shift all the time for personal reasons, and they change shifts. Changing shifts backwards (days to nights to evenings) is what is usually done, because this requires less personnel. Biologically, however, this is the wrong thing to do: Shifting forward is what should be done. And the number of days on a given shift should be the maximum possible, one month or more being preferred.

What do most shift-oriented professions (e.g. police, nurses) do? They shift backwards once per week, about the worst thing one can do to his body. About the only thing worse than that is to have no set schedule at all. Guess which profession does that? You got it, railroaders (apart from the lucky ones who work Amtrak).


Mark D. Bej, M.D.
bejm@eeg.ccf.org +216-444-0119
1996.05.07