Monday, March 21, 2011

Health markers varying inexplicably? Do some detective work with HCE

John was overweight, out of shape, and experiencing fatigue. What did he do? He removed foods rich in refined carbohydrates and sugars from his diet. He also ditched industrial seed oils and started exercising. He used HealthCorrelator for Excel (HCE) to keep track of several health-related numbers over time (see figure below).

Over the period of time covered in the dataset, health markers steadily improved. For example, John’s HDL cholesterol went from a little under 40 mg/dl to just under 70; see chart below, one of many generated by HCE.

However, John’s blood pressure varied strangely during that time, as you can see on the chart below showing the variation of systolic blood pressure (SBP) against time. What could have been the reason for that? Salt intake is an unlikely culprit, as we’ve seen before.

As it turns out, John knew that heart rate could influence blood pressure somewhat, and he also knew that his doctor’s office measured his heart rate regularly. So he got the data from his doctor's office. When he entered heart rate as a column into HCE, the reason for his blood pressure swings became clear, as you can see on the figure below.

On the left part of the figure above are the correlations between SBP and each of the other health-related variables John measured, which HCE lists in order of strength. Heart rate shows up at the top, with a high 0.946 correlation with SBP. On the right part of the figure is the chart of SBP against heart rate.

As you can see, John's heart rate, measured at the doctor's office, varied from 61 to 90 bpm. Given that, John decided to measure his resting heart rate. John’s resting heart rate, measured after waking up using a simple wrist watch, was 61 bpm.

Mystery solved! John’s blood pressure fluctuations were benign, and caused by fluctuations in heart rate.

If John's SBP had been greater than 140, which did not happen, this could be seen as an unusual example of irregular white coat hypertension.

If you are interested, this YouTube video clip discusses in more detail the case above, from HCE’s use perspective. It shows how the heart rate column was added to the dataset in HCE, how the software generated correlations and graphs, and how they were interpreted.


Kock, N. (2010). HealthCorrelator for Excel 1.0 User Manual. Laredo, Texas: ScriptWarp Systems.


Jenny said...

Ned, I fear you are drawing a false conclusion from the correlation. In fact, when people are low in potassium their blood pressure may rise, and many people on low carb diets will become slightly potassium deficient.

A sprinkle of potassium salt substitute can correct this. Other symptoms are leg cramps, and, yes, a raised pulse. But it isn't the pulse causing the blood sugar spike, it's the low potassium.

Ned Kock said...

Hi Jenny. Fictitious John’s data is based on real data, with some error added to make it untraceable. The person was on a high carb version of a paleo diet, so I doubt potassium deficiency was the reason for the heart rate and blood pressure issues.

Nevertheless, you make a very good point regarding some forms of low carb dieting, which may explain a number of issues often blamed on other things (e.g., ketosis). In fact, potassium deficiency may well be one of the key reasons behind the so-called Atkins “induction flu”.

David Isaak said...

White coat hypertension is a huge problem--as are lousy measurements in doctors offices. Put them together and you have a vast number of unnecessarily medicated people. A researcher in this area, and a past president of the AHA, has stated that, far from being "the gold standard," measurements in doctor's offices are probably the most unreliable indicators of blood pressure.

It actually isn't clear that medication for hypertension is a good thing anyway. In an important study of diabetics, they lowered one group's somewhat elevated blood pressure with drugs, and left the other group untreated. No difference in mortality or morbidity between the groups. None.

Hypertension isn't a good thing, but lowering it with drugs may be the equivalent of painting a dead lawn green--it looks better, but isn't any healthier.

But, of course, the point of the post wasn't about blood pressure, but about how correlation analysis can allow you to discover underlying connections. I only wish I had a doctor that cooperative!

Ned Kock said...

Hi David. Yes, I often see people going to the doctor and getting a pill for something - hypertension, high cholesterol etc. Soon they have some other problem, caused by the pill, for which they get another pill. And this goes on.

They never attack the source of the problem, and get increasingly sicker.

HCE is not a panacea, but it can help people identify the source of a problem, and quite effectively.

One user recently found out that several problems she was having were caused by lactose intolerance, just because the software showed a very high correlation between milk intake and various negative health “perceptions” (which she measured on a Likert-type scale; e.g., 1 to 7).

Another found that nut consumption (excessive) was tied to some strangely messed up markers, including lipids, but in a delayed fashion.

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