High blood pressure is characterised in two ways:
Essential Hypertension - No obvious cause
Secondary Hypertension - High blood pressure as a result of another medical issue.
Secondary hypertension is uncommon and accounts for about 5 - 10% of all cases of high blood pressure. The causes of secondary hypertension include obstructive sleep apnea, kidney diseases, adrenal tumours or congenital heart defects.
Secondary hypertension is not rare, but 90 to 95% of all cases of high blood pressure is considered to be ‘Essential Hypertension,’ i.e. unexplained1.
But let's take a step back and consider what that means.
High blood pressure is the risk factor associated with the most deaths per year worldwide2.
It is such an important risk factor that it accounts for over 40% more deaths than smoking.
And 90 to 95% of the cases are termed ‘Essential’ or ‘Unexplained’.
Yes, we know that high blood pressure drives the risk, but to say that we do not understand what is causing the high blood pressure in the first place seems somewhat insane.
Genetic factors undoubtedly play a role but are unlikely to account for most cases3.
Let’s look at what other factors might be driving higher blood pressure levels and see if all of it really is ‘Unexplained’.
Overweight/Obesity
39% of adults worldwide are overweight or obese4.
There is a clear relationship between increasing weight and blood pressure5.
Excess weight is a major component of ‘Unexplained’ high blood pressure.
Alcohol
Alcohol use is the 5th leading risk factor for causes of death in the United States6.
There is a direct relationship between alcohol intake and blood pressure7.
To be clear, the highest risk is associated with the highest intake.
But the risk starts to increase from the very lowest levels of alcohol intake.
Physical Activity & Fitness
There is a clear trend towards increasing blood pressure over an individual's lifetime.
However, those in the highest fitness levels stay in the normal blood pressure range for the longest period of time8.
Although blood pressure is likely to increase as you age, it is not inevitable.
The Tsimane Tribe of Bolivia has an average systolic (Top Number) blood pressure of 120mmHg, which is entirely normal. And this includes adults up to 80 years of age.
For those up to 60 years of age, the average systolic blood pressure is only 112mmHg9.
Insulin Resistance
There is a linear relationship between worsening insulin resistance and higher blood pressure.
As insulin resistance worsens, so does blood pressure10.
When evaluating those with ‘Essential’ hypertension, it is apparent that they have much higher fasting insulin levels and HOMA-IR scores, all reflective of worsening insulin resistance.
In essence, their ‘Unexplained’ high blood pressure is not so unexplained after all.
Let’s also look at the factors we already discussed:
Excess weight is associated with insulin resistance.
Excess alcohol intake is associated with insulin resistance.
Physical inactivity is associated with insulin resistance.
Starting to see a pattern?
There are likely to be multiple other factors at play when it comes to essential hypertension.
But for a risk factor that accounts for the most deaths worldwide, saying it is just ‘Unexplained’ or ‘Just the way it is’ is not a good strategy for reducing cardiovascular risk.
If you have high blood pressure, the likelihood is that it falls in the ‘Essential Hypertension’ category.
By definition, this means it is unexplained.
Do you really think so?
I think not.
Secondary Hypertension: Discovering the Underlying Cause. Am Fam Physician. 2017 Oct 1;96(7):453-461.
https://ourworldindata.org/causes-of-death
Essential hypertension. Part I: definition and etiology. Circulation. 2000 Jan 25;101(3):329-35.
https://ourworldindata.org/obesity
Association of Body Mass Index With Blood Pressure Among 1.7 Million Chinese Adults. JAMA Netw Open. 2018;1(4):e181271.
https://ourworldindata.org/causes-of-death
Association of Habitual Alcohol Intake With Risk of Cardiovascular Disease. JAMA Netw Open. 2022;5(3):e223849.
Effects of cardiorespiratory fitness on blood pressure trajectory with aging in a cohort of healthy men. J Am Coll Cardiol. 2014 Sep 23;64(12):1245-1253.
Very Low Prevalence and Incidence of Atrial Fibrillation among Bolivian Forager-Farmers. Ann Glob Health. 2021 Feb 16;87(1):18.
Comparison of Fasting Insulin Level, Homeostatic Model of Insulin Resistance, and Lipid Levels between Patients with Primary Hypertension and Normotensive Subjects. Rambam Maimonides Med J. 2022 Apr 26;13(2).
Interesting analogy
Another excellent article. Thank you Dr Barrett!