
Caffeine at night does more than keep you up late - spking
http://www.usatoday.com/story/news/health/2015/09/17/caffeine-night-does-more-than-keep-you-up-late/32548551/
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rainer_muell
For anyone wanting to skip the chain of crap articles and derivatives, those
are the sources:

[http://stm.sciencemag.org/content/7/305/305ra146](http://stm.sciencemag.org/content/7/305/305ra146)

[http://www.colorado.edu/news/releases/2015/09/16/caffeine-
ni...](http://www.colorado.edu/news/releases/2015/09/16/caffeine-night-delays-
human-circadian-clock-0)

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retroam
Wish the study was not behind a paywall but...5 human subjects?

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bildung
_> Wish the study was not behind a paywall but...5 human subjects?_

Its an experimental study, the number of subjects isn't really that important.
I can't access the full text, either, but I assume they did an ABAC test
pattern (control, treatment caffeine, control, treatment caffeine + bright
light) or something similar with all 5 subjects simultaneously.

Generally speaking, you really only need many participants for field studies,
e.g. situations where you cannot control most variables beside treatment
itself. The assumption is that the Law of large numbers takes care of equal
distribution of those confounding variables between treatment group and
control group.

~~~
chatwinra
"Its an experimental study, the number of subjects isn't really that
important."

I'd be interested to understand why this is? My logical reaction would be that
it's always important - as a crude example, surely doing an experiment on
every single human on Earth would give you much more accurate results that on
say 100 people, because you'd be sure to have covered all the innate variables
that exist when experimenting with humans? (different metabolisms, etc)

~~~
tel
Depends on what kind of generality of statement you're trying to make. Here,
the generality might be a cause and effect one in which case you're attempting
to generalize over possible future treatments and you attack detractors who
might yell "that was a fluke!" or "it wasn't the caffeine, but instead the
presence of the doctor!". To do this, you design an experiment which carefully
controls for all expected irrelevant interactions and then show a response
which is significantly different from random variation.

You end up limited, as you note, to your population. 5 people won't defeat
detractors who believe that this effect is limited within some, e.g.,
metabolic profile but it ought to give them serious food for thought as to how
wide the affected metabolic profile actually is.

If these 5 volunteers were chosen at random, then the potential generality of
effect can still be large as a detractor would be fighting, at best, with the
notion that the 5 chosen were circumstantially susceptible to this effect (as
compared to a study of convenience where one might believe that "college
students" or "hospital volunteers" are especially susceptible).

So, in a certain sense, testing every human on earth improves the power of the
statement you can make (not really its "accuracy" though maybe its
"precision", in a sense), but in many other ways that may be too expensive for
the kind of result the author seeks.

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johnbellone
If only caffeine kept me up during the day nowadays. I cut back to two mugs a
day and am seriously dragging. Although, anecdotally, I have noticed drinking
a substantial amount of water does keep the lights on. I wonder if it
similarity does so in the evening?

~~~
unoti
I've had the same issue and here is what worked for me. You might want to work
on cutting back to zero caffeine, and work on drinking plenty of water and
doing general diet improvement. If you're eating and drinking lots of sugar
that can give you uneven energy levels throughout the day. Some grains like
rice or toast in the morning for energy. Eating meals and/or snacks every 2-3
hours, and getting away from your screen for a mental break in the afternoon,
combined with a healthy diet and some exercise cured me of my late afternoon
sleepiness problem.

~~~
wpietri
This matches my experience. Kicking caffeine was a pain, and ditto for refined
carbs. But off of those, my energy levels are very even throughout the day. I
also have automated my house lights [1] so that they mimic a day-night cycle
in brightness and color. Afternoon sleepiness is not a problem for me anymore.

[1] [https://github.com/wpietri/sunrise](https://github.com/wpietri/sunrise)

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ArtDev
Caffeine at night does nothing to me. I can finish my coffee and fall straight
asleep. I do it all the time, I sleep like a log.

A sample size of 5 is way too low.

If 15% of the population does not have sleep effected by caffeine at all,
there is a good chance that this study missed people like me completely.

~~~
pessimizer
I can do the same, and I'm an extremely irregular coffee drinker. A lot of
people in a lot of cultures regularly have coffee after dinner to aid
digestion. I think whether you stay up or not after coffee drinking is largely
a matter of expectation:
[http://www.bris.ac.uk/news/2010/7051.html](http://www.bris.ac.uk/news/2010/7051.html)
"Coffee consumption unrelated to alertness" [2010]

sample size: 379

People just think that they're better reporters of their own conscious
experience than they are.

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DyslexicAtheist
autoplaying video blaring out of my speakers, wtf

~~~
metasean
and command-+ (mac) doesn't increase font size.

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sageabilly
This is really awesome to hear. For years and years I have thought I was
probably just weird or anxious because if I have caffeine later than about
noon I have serious trouble getting to sleep that night (bedtime around 10pm).
It's nice to know that there could possibly be a reasonable physical cause for
this and it's not just all in my head.

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MrJagil
I wonder if amphetamines and similar substances work in the same way. On speed
for instance, people can stay awake and party for days on end without sleep;
that would result in a tremendous push on the circadian clock, though I have
an inkling it's not simple subtraction and addition.

~~~
Raphmedia
Taking "speeds" will have a huge impact on your body. Most people that abuse
of such substance will find themselves in some sort of chemical induced
depression. Your body will stop giving you pleasure responses, nothing will
seem worth doing or living.

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pessimizer
Caffeine doesn't keep you up late: "Coffee consumption unrelated to alertness"
[http://www.bris.ac.uk/news/2010/7051.html](http://www.bris.ac.uk/news/2010/7051.html)
[2010]

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6d6b73
In 20 years, we will finally realize that humans evolved to drink only pure
water.

~~~
debacle
Evolution is a result, not a method. Nothing ever evolves _to_ do anything.

~~~
frankzinger
Wow, is that really how you read your parent? I thought his meaning was
crystal clear. Why just assume he doesn't understand evolution?

~~~
recycleme
He's not wrong. He's correcting the improper use of the word. However, I would
say evolution has results but is actually a process.

~~~
debacle
Yeah, evolution is definitely a cycle, but it can also be a state (mankind's
current state of evolution). Maybe I could have been more clear about that.

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dsfyu404ed
>volunteers who drank a double espresso three hours before bedtime experienced
a 40-minute delay of the melatonin surge.

>double espresso three hours before bedtime

>double espresso

>three hours before bedtime

Somebody get the CNN on the phone, this is groundbreaking work right here!!

