Wednesday
Jan112012

Electric Blankets

I'm posting this because it has me puzzled. As always, I'd love feedback and people's thoughts please, either in the comments section of this blog or via Twitter @Hypnagog

After seeing that my temperature dropped in REM sleep and caused me to wake up, I decided to get hold of an electric blanket to see if that could go some way to stabilising my temperature at night.

Before I carry on, this post is not an attack on electric blankets, nor their manufacturers, and I post the following findings as inconclusive and for discussion.

I fitted the blanket beneath my bedsheet, switched it on to preheat the bed (as shown in the instructions), then got into bed and turned it onto a maintenance setting.

I remember during the night that I was warm, too warm. I remember leaning over and turning it down to its lowest setting and still being uncomfotable, but I did sleep, and from memory it was most of the night.

However...

When I looked at the Zeo data I found that I had almost no REM (5 mins) and that it was replaced by wake.

I was tired when I woke, so it seems to fit. REM rebound the following evening wasn't significant, although I did enter REM before SWS.

Possible Causes?

I did wonder if the electromagnetic field given off by the blanket could have either affected me, or the Zeo's detection of REM. 

Akerstedt et al (1999) showed that a 50-60Hz field can distrupt sleep with all of the following reduced: total sleep time (TST), sleep efficiency and stages 3+4 slow wave sleep (SWS). However, REM wasn't reduced.

It could be that with such a disturbed night there was little chance of hitting REM but that seems unlikely to me as my experiment with REM deprivation shows that REM is desparate to occur (and can even happen at sleep onset if severely deprived).

I do have a couple of Gauss Meters, so the following evening I checked the blanket out. Admittedly this was with the blanket up to it's highest setting (a setting that you would only use for pre-heating, not sleeping), but as expected there is an electromagnetic field around the blanket.

The blanket didn't give off a field until I placed my hand on it (simulating someone laying down on it).

This is no surprise as everything gives off an EMF field: low energy lightbulbs, microwaves, TVs, computers, WiFi, even us to a degree. This isn't going to turn into a jumping up and down blog post demanding that we all live in Faraday Cages but I did wonder if there was an link.

If EMF is to blame, then my instinct says that the blanket affected the measurement of REM rather than the REM itself.

Another possibility is that there is a link between reduced REM and increased body temperature, such as in the case highlighted here (a fever causing reduced / disturbed REM sleep).

Could it just be that the temperature disturbed me during the night, after all I do like the bedroom to be cold?

If I had to guess why this would only happen in REM, I would have to speculate that this is because the body doesn't regulate its temperature well during REM and becomes largely poikilothermic, so rather than waking because I was too cold, I was waking because I was too warm. This would suggest that I did go into REM but that it was too fragmented to be detected by the 30 second epoch of the Zeo. I would suggest that REM that is that fragmented is next to useless as far as restorative sleep is concerned.

 

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