Musings of a Restless Mind

Or Blood Pressure is Stupid!

I came across an article that insisted that 1 of 4 indicators are present in over 90% of those who will eventually have strokes or heart attacks. Now, as a reformed statistician, the first thing I thought of when I read that headline is how stupid that study must be. You see, I could infallibly predict that 100% of those who had a heart attack today, or any day, breathed oxygen on that day. So, want to not die of a heart attack? Just stop breathing. Case solved. But then it may only be the headline writer that makes it sound stupid, so I checked. Here are their 4 criteria.

• systolic BP ≥120 mm Hg or diastolic BP ≥80 mm Hg or BP-lowering treatment
• total cholesterol ≥200 mg/dL or lipid-lowering treatment
• fasting glucose ≥100 mg/dL or diagnosis of diabetes or glucose-lowering treatment
• past or current smoking—at any visit before CVD.

Now the caveats at the end of each are to exclude good numbers from anyone who has “artificially” lowered their risk factors by the miracles of modern medical treatment. That caveat has its own problem, but I’ll skip over that. Just put the word “untreated” before each of the first 3 conditions to make it more clear, but we don’t need to go into that. I’ll also skip over the middle two factors because those measurements aren’t as ubiquitous as blood pressure and smoking.

The smoking measure has its own problem because they say having ever smoked before developing cardio-vascular disease (that’s what they mean by CVD). So if you took that one puff on a joint in college, you are already a big cohort of the 90%. Official smoking rates for the US say 42% of the adult US population smoked in 1965, and, according to life expectancy statistics, a lot of us are still alive. Smoking’s way down to about 15% of the US population today, but that only means you have to add that 15% to the 42% (minus the percentage of those who have died since 1965), making it over 50% of the US population who have ever smoked and are still around in the Year of Our Lord 2026. Remember, that’s what they’re saying when they say past or current smoking. So that probably accounts for half the 90% prediction right there, and you can’t fix that unless you have a time machine. If you ever smoked, chances are (at least partially), you’re part of the doomed.

But what I really want to talk about is blood pressure. The first question I have is how much of the US population has blood pressure above 120mm Hg (that’s 120 millimeters of mercury because the first way they measured blood pressure was with the level of mercury in a cylinder attached to the blood pressure cuff, but you don’t have to know that anymore). The answer to that question is–nobody knows. They’ve done studies with up to 5,000 patients of varying ages broken into 5 age cohorts, so, theoretically, n=1,000 as we say in the stat world. It’s accepted practice that using a baseline of 1,000 means fairly high confidence levels for statisticians, so there’s that.

There is another problem though. I donate blood (platelets and sometimes plasma actually) every 2 or 3 weeks. To gauge my eligibility, they take my blood pressure, pulse rate, and hemoglobin count every time. So I have a track record of 43 blood pressure readings going back two and a half years. And my systolic BP ranges from a low of 94 to a high of 162, with an average (mean) of 131. To be specific my counts are:

Less than 120: 8

120-129: 10

130-139: 12

140-149: 9

150 or higher 4

So, do I have high blood pressure, low blood pressure, or just random blood pressure? I’ve even taken my own blood pressure multiple times at 3 minute intervals and come up with wildly different readings. I’m willing to concede that some people have chronic high blood pressure, and probably a few have chronic low blood pressure, but, as you can see, we’re using an instrument that, even if accurate, returns wildly fluctuating readings depending on more circumstances than we can enumerate. My point is that it’s unethical to make medical judgements using blood pressure unless you consistently test two standard deviations from the norm as we statisticians say. Basically that’s the outlying 2% on either side of the bell curve. (There’s a lot of caveats to that statement about normal and abnormal distributions, but just take my word for it.)

Medical professionals have a similar problem with Body Mass Index (BMI). A statistician invented that stat by dividing your weight in kilograms by the square of your height in meters. I know, I know, why would he do that? Because it made for nice numbers between 16 and 40. He counseled that it was only useful to compare large populations, like seeing how fat the Danes are compared to the French. For individuals, it’s very crude. Unlike blood pressure though, it doesn’t fluctuate wildly throughout the day. So there’s that. What it doesn’t do is take into account body type. I’m 6’2” and I have the body type that naturally carries more weight. Back when I was young and in shape (and weighed 205 pounds), I had a tailor ask me, was I a football player because I had a 17” neck and a 34” waist. Currently, after 45 years sitting at a desk writing code and now stories, I’m overweight at 245 pounds. The problem is that the BMI would classify me as obese and even the 21 year-old me that the tailor was astonished by, as considerably overweight.

So what do I recommend? Pay attention, and be honest with yourself. You know if you’re not healthy, although it’s easy for you to deny it. Your doctor sees you twice a year for 5 minutes. You live with yourself 24/7, so you know better. Just don’t kid yourself.

P.S. I let AI suggest a title to lure more readers in, so my title is the subtitle. If I tricked you, blame AI 🙂