can tiredness be quantified?
July 22, 2005 5:47 PM   Subscribe

is it possible to measure exactly how tired someone is? how would that be done?
posted by ronenosity to Science & Nature (9 answers total)
 
I suppose you could measure how much adenosine diphosphate there is in a person, compared to their highest (presumably right after they wake up) amount in their blood.

ADP is the product of the breakdown of ATP (adenosine triphosphate) which is one of the primary "energy carriers" in the body's metabolic system. (That is, ATP stores and carries chemical energy from one system to another.) Throughout the course of the day, ATP levels are decreased as ATP is broken down into ADP (by ATPases). Of course, keep in mind that the body is also re-storing its reserves of ATP at the same time so that you can function later in the day, just the same as in the morning.

I suppose this is one possible answer to your question. Any biochemistry folks out there, feel free to correct anything I've gotten wrong.
posted by ruwan at 6:00 PM on July 22, 2005


It may be helpful to define and agree upon your definition of tired. That is, to make a distinction between tired, and fatigued, where tired is feeling the need to sleep, and fatigued is lacking energy.

a common way of quantifying tiredness is a multiple sleep latency test (MSLT) which is simply a series of naps where time to sleep onset is measured. Generally a mean sleep onset of less than 5 minutes is considered significant
posted by skinnydipp at 6:10 PM on July 22, 2005


Ask them to rate how tired they are on a 1-10 scale.

Be sure to distinguish between sleepy tired and exhausted tired. This is basically how the effectiveness of anti-depressants is measured.

That said, there are some brain hormones associated with sleepyness. I don't remember what they are off the top of my head.
posted by delmoi at 6:57 PM on July 22, 2005


Some technology has been developed for fighter pilots that measures eye movement. Certain patterns (say, closing your eyes for longer than just a blink?) indicate fatigue tiredness and set off alarms.
posted by Alt F4 at 7:06 PM on July 22, 2005


What about reaction time? -- that can be measured. Would that be a help in determining tiredness?
posted by Miko at 8:08 PM on July 22, 2005




Best answer: IANAD, but MSLT does indeed seem to be the way to determine tiredness, or more specifically, sleepiness, for persisting situations ("I'm always sleepy in the middle of the day, even though I get 8 hours at night").

If you were looking for "how tired are you right now?" I think the trouble is that this is entirely subjective, in which case delmoi's answer is probably best. People just react too differently to the same physical conditions for a standardized physical measurement to be useful.

On a personal note, if an MSLT is what you are looking for, be warned that they are not fun. My wife had to have one, and "you are allowed 20 minutes to fall asleep 4 to 6 times during a day" omits that a tech will wake you up 4 to 6 times, just when you had managed to ignore the videocameras and electrodes and finally take a nap. It's like camping and realizing that the rock you thought wasn't under your sleeping bag is the suddenly much sharper rock that you keep rolling onto every half hour all night. Not even a post-test MSLT sandwich (Meat, Sprouts, Lettuce, Tomato) will alleviate the inevitable crankiness.
posted by rossmik at 12:31 AM on July 23, 2005


Quote by delmoi: "That said, there are some brain hormones associated with sleepyness. I don't remember what they are off the top of my head."

Melatonin?
posted by IndigoRain at 11:42 PM on July 23, 2005


The sleep specialists I work with usually talk about giving some one a brief questionaire called the "epworth sleepiness scale", but that's more of a general indicator of poor sleeping habits than a test of how tired someone is right now.
posted by cosmicbandito at 11:48 PM on July 23, 2005


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