Blood pressure vs body temperature

A snowHead

I did a search on the internet a few years ago for data on how blood pressure varies by temperature. I found one or two studies which suggested that some people are more sensitive than others. Overall though, it suggested a relationship of systolic blood pressure would decrease by 0.3mmHg times the increase in room temperature indoors in centigrade.

This was not really helpful to me, and it also suggested diastolic was less related to room temperature. In my understanding of how blood vessels close up, I would have thought it would have had a similar effect. However, perhaps their studies were on a bigger sample and normalised for other factors which I have not removed. (my graph is a one way analysis, theirs may have stripped out interaction effects)

Anyway, over that time I decided to measure my blood pressure in different room temperatures with my body temperature and some other data. I am still gathering data particularly at the extrema of body temperature and room temperature.

So far I have found that my body temperature increases with room temperature more or less linearly. Both diastolic and systolic blood pressure decrease with increases in room temperature and body temperature. (as you might expect)

However, I found that the rate of change is much greater for me than the study on the internet. More than 3x-5x greater effect on my diastolic and systolic than the average in the study.

What was also worrying was that my body temperature (using my method of measurement) could almost be hypothermic without me even feel like shivering.

My method of body temperature measurement resulted in an average temperature of 36.4 C which could be on the lowish side. I measured it orally, and so other methods may give a more accurate measurement of inner body temperature. If you add 0.5C to my temperature measurements it should be about right.

One to think about when you are out skiing for a long time in cold weather. Particularly, for people over 50 for whom cold "is said" to have a more significant impact on body temperature (I have not seen anything which definitively proves this hypothesis, other than my own data)

My systolic is usually 40-50 above my diastolic. (probably closer to 50 on average) The systolic graph is similar, but slightly lower gradient.

Shocked

https://www.ncbi.nlm.nih.gov/pubmed/17496471

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Well, the person's real but it's just a made up name, see?

I think I will wear a scarf more often in cold weather, and take more coffee breaks in warm up huts.

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@Bigtipper, very interesting. This might be useful - https://www.bbc.co.uk/programmes/w3cswk3g In summary, core body temperature may be subject to more variability across the population than was previously understood. You may be a person whose average core temperature is lower than what was previously understood to be "normal". I don't know anything about blood pressure so not sure that's helpful!

Any excuse to drink more coffee sounds like a good one to me...

[edited to get hyperlink working]

Anyway, snowHeads is much more fun if you do.

@Sideshowbob, body fat percentage may have something to do with it (mine is very low), also I am older than the average age in the summary which also affects the body temperature. However, my blood pressure appears to be lower than average for my age, and is lower than it was when I was 20 years younger on average!

Your link is to a page which is no longer exists.

However, I think the years when I spent sleeping in the Tignes Val Claret car park at -15C had an effect on my reaction to cold. Makes me very sensitive to cold temperatures, causing my blood vessels to shut rapidly in the event of cold. Measuring my body temperature by oral temperatures may be too inaccurate, and rectal measurements may be necessary to get to core body temperature which may be higher. (I think I will use a different thermometer for that)

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@Bigtipper, remove the full stop at the end,

Then you can post your own questions or snow reports...

@Hells Bells, I get that now but I need to sign in and I am very wary of who I give one of my email addresses to. (I get too much spam as it is, and my person details are not secure enough so I have to make up fake names : -even though they know my IP address I am loathe to link it to real details which makes a mokery of their survey data)

The thought of what happens when I have a fever to my blood pressure when I look at the graph I produced suggests that I may become hypotensive and prone to fainting. I have not had a fever at any time in the last 2 years so I have no data on this scenario. Perhaps it is not a linear relationship and may be a flatter relationship above 37C?

After all it is free

So I can download the mp3 file without registering, and I listened to the podcast. It is something I was aware of, that the method of measurement of body temperature and the calibration of the thermometer is important in accuracy.

I do not get temperatures or fevers in recent years, the only time I felt like I had a minor headache my temperature was 36.7C. This either confirms the podcast in that some people can have a fever at temperatures which appear normal, or that my thermometer is not accurate at oral temperature reading compared to rectal or aural. Armpit measurements are known to be much lower, and I have not even bothered with that as it is old medicine.

Error bars would be helpful on that chart.

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I believe the R2 figure on the graph is an indication of goodness of fit of the data to the straight line. It is lower for the systolic graphs, and for graphs with room temperature. However, choosing the best graph based on goodness of fit data is data trawling. There is not yet enough data for me to fit any estimation of standard deviation. I could put the actual standard deviation, but that may be misleading as this does not take into account the measurement errors. In other words I need separate study, and more data to derive likely error data.

The best way to do it currently, would be to draw some lines so that most of the data points fit in the area between the lines. However, not sure there would be much more benefit of that than just including all the data points and the fitted line.

Join the dots?

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@Bigtipper,
I really think you should check what colour clothes you are wearing as well.
http://www.all-science-fair-projects.com/print_project_1078_134

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What is the measurement accuracy of the thermometer? 0.1C?

You know it makes sense.

@Bigtipper, With all your spreadsheets of alcohol consumption, blood pressure and temperature don't you think you are focusing rather too much on your vitals and on your health in general?

Otherwise you'll just go on seeing the one name:

A snowHead

As I said in the OP, I am still collecting data. Indeed there are many data points with only one entry. The clusters around my average body temperature of 36.4 suggests that this is where most of the readings will come on average. The outliers where the room temperature is low only occur when it gets cold. As I do not get a fever regularly, it is difficult to find any figures on that.

Over time I will collect more data, and the slope will change, as will the R2. However, at the moment it indicates that there is a possible relationship which has been proven with more substantial data. Obviously I need more data to prove the specific gradient in my case compared to the average. This will take more time to collect, it cannot be done overnight. (although that is when my body temperature tends to go down)

The problem with using systolic is that it tends to fluctuate for other reasons than temperature. It can be more volatile than diastolic in my experience. In measuring diastolic, it gives a better indication of the effect of temperature without any other influencing factors.

A snowHead

@Bigtipper, why are you doing this?

Well, the person's real but it's just a made up name, see?

@holidayloverxx, sometimes there is no answer other than it is there. Knowledge about my body helps me look after it better. Knowledge about the population average, allows me to compare how "normal" or "supra-normal" I am.

I think the true answer is because "I can".

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@Bigtipper, Ah well, at least there's a reason Laughing

Anyway, snowHeads is much more fun if you do.

With the cold weather arriving this November, and with the forecast for a long sub zero stretch, I have started recording my blood pressure and body temperature again in order to get more low body temperature readings. 35.7C this morning after I had warmed up! Fitted it on the graph with my blood pressure reading, and it is pretty close to the fitted line. R2 is reducing with this extra reading.

I expect I might get quite a few more cold readings this month.....

Brrr..

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How do you eliminate all the other factors to get any meaningful data? Time of day, time of eating, thermometer technical accuracy, thermometer positioning (rectal is probably the only way to get a vaguely accurate result), natural variation between days, sleep timings, alcoholic consumption, etc etc. My understanding is that cold weather has almost not effect on core temperature until you get close to hypothermia/hyperthermia. Think of a large piece of meat in the oven. The temperature gradient is such that even a massive temperature differential takes a long time to raise the temperature in the middle of the joint.

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I do not eliminate any other factors. I am doing a one way analysis. I do not make any recordings when I have alcohol in my system. Some of the higher readings with low body temperature will be because I will generally be making these readings in the morning, and the lower readings will generally be done in the evening when I have higher body temperature and the room is warmer.

I would guess that means that when I take a reading when body temperature is high in the morning, it will not be as reduced as it is in the evening when my body temperature is warm. However, I am only doing it to get a rough idea of the relationship. The exact relationship will be different due to the interaction effects.

Body temperature varies. My body temperature is lower when I am cold, and higher when I am warm. I am not sure where you get the idea that there is no relationship between body temperature and room temperature. There is definately a direct correlation between body temperature and room temperature in my data.

When I take blood pressure and body temperature, I will generally have been in the same state for some time. I do not ramp up room temperature, and then take blood pressure. I take it when the room has been warm for hours, and I have been in it.

A one way analysis gives an indication of the relationship. It does not strip out the fact that I am generally recording cold body temperatures in the morning, and warm body temperatures in the evening. This may reduce the gradient. However, it is unlikely to eliminate the gradient fully.

I can test some of the other factors, but I doubt they will be very significant.

The accuracy of temperature readings is not important. Consistency of measurement method is important. I am doing it the same way each time.

After all it is free

@Bigtipper, The correlation between being cold/hot and core temperature is pretty limited. If your readings appear to correlate then I’d suspect it has more to do with the reading technique (orally I guess) than a genuine change In core temp. The temperature of your mouth can indeed vary significantly depending upon a whole range of factors with external temperature being a major factor. Trying sticking it up your bum and see if you get the same correlation.

@foxtrotzulu, What is important is that the correlation between the way I measure body temperature and blood pressure is not pretty limited. Also, body temperature using my measurement and room temperature is not pretty limited.

If you want to stick something up my bum and say that my core temperature is not varying, but my peripheral temperature is varying, then that is interesting but not relevant to the question I am addressing. It is addressing a different question, regarding whether core temperature varies when you are cold or hot.

You seem to be more interested in determining hypothermia. I am more interested in finding a way of explaining to myself the volatility of my blood pressure. Finding a variable which does not vary is not very interesting in this regard. Finding one which is correlated is interesting. Do you see my point?

https://en.wikipedia.org/wiki/Human_body_temperature

The figures given in wikipedia suggest 5.6% spread in body temperature readings orally, and a 2.2% spread when done rectally. Therefore, there is more volatility in oral readings, than rectal readings. However, there is still volatility in the rectal readings, and so it would presumably give a similar result. This appears to be because of the normal change during the day when core body temperature varies by up to 0.5 degrees centigrade. (or 0.8 degrees centrigrade if measured rectally)

quote from the above link:

"Body temperature normally fluctuates over the day following Circadian rhythms, with the lowest levels around 4 a.m. and the highest in the late afternoon, between 4:00 and 6:00 p.m. (assuming the person sleeps at night and stays awake during the day).[10][12] Therefore, an oral temperature of 37.3 °C (99.1 °F) would, strictly speaking, be a normal, healthy temperature in the afternoon but not in the early morning.[12] An individual's body temperature typically changes by about 0.5 °C (0.9 °F) between its highest and lowest points each day.[10][12]"

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Using my method of measuring body temperature (consistent with the graph early on in this post), I recorded a temperature of 37.5C on the evening after my first injection. (for coronovirus 19 immunisation) This is 1.1C above the average for me, and a never before recorded level for me using my method.

I did not bother measuring my blood pressure, as it would have been distorted by my immune reaction.

When I went to bed that night, my teeth were chattering briefly and I shivered until the electric blanket kicked in.

I felt slightly tired the next day, and had a slight pain in the arm. However, these were expected normal reactions to the injection, and were gone by day 3.

It is interesting to note how hot I felt when taking the reading. (for future reference) The high body temperature was gone the next day, when it read 36.3 C in the morning.

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Second covid vaccination yesterday lunchtime. Immediately felt slightly off, temperature peaked at 36.7C at 7pm, back down to 36.1C by 10:30 pm after the football. (so well below the 37.5C after first jab) 36.7C is the highest recorded in my graph at the start of this thread (so within my normal range), which can occur when the room is warm and I am warm.

This morning I feel fine. So, some effect but much less than first jab. Last time I stopped jogging for a day as I was tired. Should be fine for a run today. snowHead

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Blood pressure vs body temperature

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