Research: Solar Activity Causes High Blood Pressure

In the Class, which I know all readers are dutifully following, bless you, I often cite Tyler Vigen’s Spurious Correlations site. It is a glorious (growing) compendium of ridiculous results blessed by Wee P-values, a form of pagan magic science has not yet eliminated. Here’s one of the recent pics:

If you say P-values have some uses, and are a valid tool in inference, you must agree that there is some sort of causal relation between soy beans in North Dakota and geothermal power in Russia. Or if you claim you reject (good pun!) this wee P because of outside evidence (however that is formed), then you have admitted you are allowed to use outside evidence—and so you don’t need wee Ps. Give them up.

The soy entry is number 2,699 in Vigen’s collection. I have for him number 2,700 in the form of the peer-reviewed paper “Potential influence of geomagnetic activity on blood pressure statistical fluctuations at mid-magnetic latitudes” by a large group of Chinese researchers (it’s relevant) led by Pengzhi He in Nature Communications Medicine.

From the Abstract:

Background Solar activity and the consequent geomagnetic activity (GMA) profoundly influence human biological rhythms and cardiovascular system functions. Although the response of blood pressure (BP) to GMA has attracted considerable attention, it is unclear whether the GMA can have an influence alone and how it occurs.

Methods In this six-year time series analysis, we collated over 500,000 BP measurements from two representative cities (Qingdao and Weihai) at mid-magnetic latitudes in China. Using various statistical methods, we analyzed the correlation between BP and the GMA (represented by Ap index) and their quasi-periodic fluctuations. Additionally, we conducted a comparative analysis of the influence of other environmental factors (air temperature and PM2.5) on BP.

Results The statistical BP level fluctuations correlate with the GMA.

GMA is measured by the Ap Index, a measure of fluctuation in earth’s magnetic field as it is operated on by certain solar forces. Blood pressure was downloaded from a hospital database.

Here is their main picture:

The blood pressure, systolic and diastolic, peak in months 3 or 4 or so and again months 10 and 11, with variation by year. The bottoms are as you see. The BP signal is a lot stronger than Ap, which only shows up, barely, in averages, peaking and bottoming at about the same months.

I won’t bother going through the details of the model, but the results are wee Ps galore, which “confirm” the correlation between BP and Ap. But what is the proposed causal path?

The occurrence of two peaks each year and the 6-month periodicity of GMA can be attributed to the occurrence of strong geomagnetic storm events that are triggered by the Interplanetary Magnetic Field (IMF). These events have a higher likelihood of occurring around the annual vernal equinox (autumnal equinox) when the IMF is aligned toward (away from) the sun. This mechanism is commonly explained by both the Russell-McPherron effect and the equinoctial effect, which are widely accepted in the scientific community. The influence of GMA on human health is believed to be mediated through direct or indirect pathways, with one potential indirect method being through primary effects in the brain that cascade downstream via the vagus nerve. Future research is required to collect the patient data where vagus nerves were removed/severed surgically (or inhibited pharmaceutically), with the aim to explore the role of the vagus nerve in mediating the effects of GMA on BP.

If you are admitted to a Chinese hospital, best put a guard on your vagus nerve (just as if you are admitted to a UK or Canadian hospital, best put a guard on your genitals and your body itself, especially if you have juicy organs).

Here from the the authors is a picture of the number of blood pressure measurements taken by month, which I’m amazed and gratified they included:

The solid lines are the BP measurements themselves, and the dashed the number of patients admitted who have codes for hypertension.

You will, I hope, see the deep dips around the 2nd through 3rd months or so, and smaller ones in fall. These are, of course, as the Chinese authors themselves know better than we, lunar New Year, the biggest holiday of the year, and mid-Autumn festival, another major holiday (but not as big).

The same thing happens here, with dips in admissions occurring at Christmas. The signal, believe or not, is particularly strong in the UK. Or was. But let that pass.

The dips in measurements corresponds to peak in the BP measures, and vice versa, meaning the sicker patients stayed in hospital during New Year and mid-Autumn festival, and so naturally had higher BPs. When in other times with major holidays the greater numbers of patients, not all in for hypertension, but incidentally having it, have lower on average BPs.

Mystery solved.

The solar signal is anyway weak, and the wee Ps don’t come until some substantial massaging of them. The causal path is suspect. There is thus no reason to believe the sun is spiking BPs.

This does not mean, I hope I do not have to say, but will, that I have proved the sun doesn’t influence BPs. It might. I don’t know. But I have shown that the claim cannot be believed from this data.

Please do not use P-values ever again.

(Incidentally, the authors would not have been helped if they followed patient time series, instead of across-patient averages. The holiday effect would surely still exist.)

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