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A comment on Ask HN: how did you fix problems with bad sleep?. Parent comment

Re:Ask HN: how did you fix problems with bad sleep? by ericb on Saturday May 31, 2008 @09:56AM (#205251)
If the 10 hour half-life were true, we'd all be Cornholio by now. A 10 hour half life means at 30 hours, you'd still have 12.5% of the caffeine in your system and at 40 hours you'd have 6.25%. I'd have coffee in me from the last week still in effect. Is there some other half life term I'm not familiar with?

In this regard, I'd go with wikipedia. There are plenty of doctors who are wrong in the world--they are only human.

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Re:Ask HN: how did you fix problems with bad sleep? by gojomo on Saturday May 31, 2008 @11:39AM (#205275)
"Half-life" by biological elimination is not precisely exponential as with radioactive decay, and may trend closer to a linear process -- as in, your liver can eliminate X units per hour, not X% of however much you've had.

Thus the (informal) "half life" of one cup of coffee could be 4 hours, but two cups could be 8 hours, and so on.

(To the extent I can track the estimates of "3.5 to 6" or "5.7" hours of caffeine half-life back to original sources, it looks like the studies were done in 1978 and 1980. Maybe modern caffeine consumption has moved to a level where linear rather than exponential elimination dominates?)

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Re:Ask HN: how did you fix problems with bad sleep? by icky on Sunday June 01, 2008 @04:45AM (#205768)
> "Half-life" by biological elimination is not precisely exponential as with radioactive decay, and may trend closer to a linear process -- as in, your liver can eliminate X units per hour, not X% of however much you've had.

Damn. I was hoping to calculate the optimal hour for a caffeine "booster" after the initial morning fix.

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Re:Ask HN: how did you fix problems with bad sleep? by DenisM on Saturday May 31, 2008 @11:35AM (#205273)
And what makes you think you don't have 6.25% after 40 hours? When I stop consuming caffeine it takes couple of days for the effect to wear off. Did it twice so far - I'm ususally off caffeine but let it slide during vacations.
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