Hypothermia - different according to normal body temperature?

[Lysistrata]

Does anyone know if someone's normal body temperature significantly affects their survival in cold temperatures? I know that the average is 37C/98.6F, but that some people have slightly lower and some slightly higher (I know mine, for instance, is lower than the average). Hypothermia is generally considered to be when body temperature falls below 35C, but if you started at a lower temperature (say 36 or 35.5), would you be more prone to hypothermia, or would you not begin to experience hypothermia until a lower temperature than someone whose normal temperature was 37?
I hope this doesn't come out as total rubbish, but I'm quite curious; all the info I've found is based on averages.

[jake-the-peg]

I don't think it's as simple as what someone's normal body temperature is.

Some humans exhibit mamalian diving reflex - which basically slows down the heart and respiration in contact with cold water.

But the biggest factor is how much fat you have.

The better insulated you are the longer it takes you to lose heat, a slight variation in your bodies normal temperature is not likely to be significant in comparison

[Lysistrata]

Thanks. I think I wasn't as clear as I meant to be. 'Prone' was a bad word, as that does suggest how quickly someone cools down and how long they can survive, which is dependent on a range of factors as you said.
What I was really curious about is whether the temperature at which someone becomes hypothermic is tied to the normal body temperature they started at, ie whether it's 'over 2 degrees C below normal temperature' rather than 'under 35 degrees C'. The rate at which someone reached that temperature would, as you said, be affected by how well-insulated they were, but I wondered if the 'dangerous' temperature was different depending on the person.

[jake-the-peg]

I think you may find that there are a number of factors and that a 1-2% difference in someones normal body temperature is masked by other issues.

There are ethical issues with getting good data on this subject.

I taught diving a decade or more ago and I believe that the primary source of data came from experiments conducted on US military volunteers who were all fit young men (and the experiments obviously were not taken to dangerous degrees)

There was/is some data based on experiments in Nazi concentration camps that were ..er taken further but again these victims were not necessally representative of normal healthy subjects.

I believe more recently there was a case of a group of divers who were clinging to the wreck of their boat. As they died someone recorded the date and time on his dive computer. The post mortems established a strong link between insulation and life expectancy.

Such are the difficulties of asking and answering such questions

[Lysistrata]

Thanks. I was aware that there are a number of factors but had wondered if anyone had managed to isolate any that related to the point of hypothermia rather than the rate of cooling. As you say though, proper experimentation and separation of the contributing factors isn't really an option!

I'm looking into a case where someone survived for 2+ hours in water of about 33F, which I thought was pretty much impossible, but his testimony seems to confirm the timing - it fits with events which can be fixed at a point in time (ie daybreak). Was wondering if anything other than insulation etc. might have contributed to his survival, though we'll never know for sure, especially since it was 97 years ago.