Science Questions

Why do I get too hot in bed after I've been drinking?

Sun, 31st Aug 2008

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Question

Sean Moore asked:

When I go to bed drunk I often find myself unusually warm in the night. Normally I get cold when I sleep but when I'm drunk I wake up at say, 3am, all hot and bothered. What's up with that?

Answer

Sarah -  Well, he did say normally I get quite cold when I go to sleep and that's quite normal because your body temperature actually drops during the night and Ciderit's usually at its coldest about two hours before you get up. 

But when you've been drinking, your liver is madly metabolising all the alcohol, breaking it down to get it out of your blood stream.  This is a really exothermic process which means it produces a lot of heat.  Your liver is actually the main heat-producing organ in your body anyway.  When it's working extra hard you're producing a lot more heat than usual.  Added to that alcohol stops you from being able to thermo-regulate.  When you're too hot, you sweat to cool down - the alcohol stops your body from being able to do that.  This combined with much more heat being produced by your liver really makes you heat up in the night.

Ben -  So it's a double whammy then.  The actual breaking-down of the alcohol produces more heat anyway and the fact that there's alcohol there means your body can't cope with that excess heat?

Sarah -  Yeah, exactly.  Although you can actually see the opposite thing in people coming out of clubs late at night.  I'm sure everyone's seen it or done it themselves: the sort of 'beer jacket' effect where you come out in a just a small T-shirt and you're not cold.  It's because the alcohol makes you less able to feel the cold.

Ben -  This is for when you've gone out and tried to avoid spending the extra pound to put your coat in the cloakroom so you just leave your coat at home.  Actually at 3am, you don't notice at all that you're losing lots of heat?

Sarah -  Exactly.  Usually it's fine but it can be quite dangerous for people who live on the street and if they drink they might not notice it's really cold so it can be quite dangerous for them.

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Alcohol causes blood vessels to dilate (vasodilator), e.g. drunk Caucasian people are often red faced.
The increased blood flow to the skin could be responsible for being too hot in bed.

If you fell asleep drunk in a cold environment (e.g. outdoors) this same vasodilation effect could cause you to become too cold (hypothermia).  RD, Sun, 3rd Aug 2008

Over the past year, my body temperature seems to rise noticeablely when I go to bed, to the point where I am taking off my sheet and finding it difficult to sleep. This happens irrespective of the room temperature and when I haven't even had a drink. What's causing this? Colin, Thu, 14th Jan 2010

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