kiwi36

This is my first message, and I respond not because I feel I know the real answer to your question - but because the "subject" really interests me.

Just a quick snapshot of me, I'm 54, male with hypertension on paternal side. 6 years ago I was obese (BMI=33) but that year (2002) started a low carb lifestyle, and currently have a BMI=24.8 and an average resting BP of 109/71. Take no medication, and have a fairly good fitness. So my quest is not to reduce BP - but to carefully monitor it for any signs I need to change my diet/lifestyle. Having only had my BP monitor for a couple of months I have found it interesting to first of all make sure it compares accurately to several other monitors and to learn about BP taking technique.

The surprising thing I first (and I think everyone else) learns about taking BP, is that it "fluctuates". It is like trying to measure the height of a child while it insists on jumping up and down!

My current method is to use a timer to take a reading every 5 minutes, after following normal procedures (sitting for 5 minutes, legs not crossed, relaxed, no talking or movement etc) I take 12 readings (1 hour). Using either EXCEL spreadsheet or suitable calculator, I "average" the results and find the "standard deviation" of the 12 readings.

The "standard deviation" gives a single value that denotes the "spread" of the values (how much they fluctuate) from the average value.

So if I take your above values we get:

140.25 / 74.25 with a SD (standard deviation) = 7.27 / 3.3

With only 4 of your readings a systolic SD of 7 is about right, I normally get over my 12 readings a systolic SD of about 4 mm Hg, so my systolic thus "fluctuates" from 105 to 113 mm Hg.

Going back through the archives here, there is one person (who I have learned a lot from) who has the name "Machaon", who seems to be the only person who uses "standard deviation" with reference to BP in this group.

I have found very little doing net searches on the subject of "normal" standard deviation with respect BP. It is usually found in surveys as a method of showing how much bp "fluctuates" over a large "group" of people rather than what you would expect with an individuals reading.

Having (for interests sake) measured the bp of a few other people, I have noticed they all have their own distinct SD of BP. In one case although the persons average systolic hardly ever moved between readings, they could have a SD of 5 for many readings - and yet sometimes up to 15 at other (less frequent times). This to me showed how taking bp can be "difficult" to do with confidence. We have a complex and sophisticated feedback system to control normal bp in the body.

I have attempted to apply a few other statistical tests (like SKEW and KURTOSIS) to my data, but I think taking only 12 readings each time is not enough data - but "standard deviation" I have found to be very useful to get to know my own bp - and to create a benchmark for my future readings.

So the subject of "standard deviation" of BP I find very interesting, and certainly would like to learn more!

Perhaps you need to gather some more data to decide which hypertension group you really belong to. I hope that helps.