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A article by Dr Edward Leatham. The views expressed here are my personal views, not necessarily consensus view.
Blood pressure management is a crucial aspect of maintaining cardiovascular health. My belief is that the best blood pressure to have in mid life for longevity and freedom from heart failure in later life, is for it to be as low as possible without having side effects. The pursuit of optimal blood pressure can be a challenging journey for many patients, who frequently ask why their blood pressure has risen over time. Many recall having lower readings in their youth and are baffled by its current elevation, despite careful attention to their diet and salt intake.
The Genetic Legacy: Salt Sensitivity and Blood Pressure Hypothesis
This story begins over 2 million years ago when most mammals (including humans) died of sepsis, injury, childbirth and accidents. Species survival created evolutionary pressure for protective systems that counter low blood pressure or ‘shock’, where organ failure occurs as a result of low blood pressure. These ‘flight, fight or fright’ pathways act to increase blood pressure in crisis and include adrenaline release, neural and blood borne pathways that cause peripheral constriction, with salt (Sodium Chloride) and water retention. Most hypertension seems to be caused by a central fault in a complex control system based in the hypothalamic area of the brain which counters shock. It is quite possible that hypertension in humans is linked to this blood pressure ‘regulating system’ being set too high (likened to a house thermostat set too high), particularly if there is genetic predisposition coupled with excessive salt consumption throughout our lives.
In regions of sub-Saharan Africa that are naturally devoid of salt, gain of function mutations occurred that helped our ancestors living in these regions to survive and propagate despite minimal dietary intake of salt. Following migration out of Africa 50-70 thousand years ago and with the arrival of salt (Sodium Chloride) as a preservative from the middle ages, the genetic and environmental triggers for modern day hypertension were set. In the Middle Ages, salt became a favoured method of preserving food, and it remains prevalent in modern diets and food processing.
These genetic adaptations are now widespread in modern society. Those fortunate enough to inherit genes that code for blood pressure that is not so sensitive to salt intake will generally remain normotensive throughout life. However, for a significant proportion of the population, perhaps related to inheriting genes tracing back to prehistoric ancestors surviving in sub-Saharan Africa, high salt (Sodium Chloride) intake while young may be sufficient to trigger physiological changes that lead to hypertension developing, especially after their second decade of life.
The interaction between genetics and dietary salt intake explains the broad range of blood pressure values we see today, heavily influenced by inherited traits. This phenomenon explains why patients with hypertension often appear to have a genetic predisposition, with one or both parents suffering from hypertension or related conditions like atrial fibrillation, stroke, or heart failure.
Blood Pressure Programming: The Importance of Early-Life Diet
Animal models of hypertension show a clear link between salt intake in mammalian early life and blood pressure later in their life. In humans dietary salt consumption during the first two decades of life may well program future blood pressure, explaining why only a small proportion (10%) of adult patients with essential hypertension are ‘salt sensitive’. Their blood pressure can be lowered somewhat by adopting a salt-free diet. For the majority of adult hypertensive patients, despite the likely importance of salt as a contributory cause of their hypertension, adopting a low salt diet as part of treatment yields disappointing results- it literally is a case of ‘too little too late’. This concept highlights the importance of reducing salt intake in children and young adults, especially in families genetically prone to hypertension. Lobbying for healthier food production practices, particularly in schools, and encouraging low-salt diets at home may be the only way that reducing dietary salt intake can significantly reduce hypertension in adult life.
The Lifelong Burden: How Blood Pressure Affects the Heart
The human heart beats around a billion times in an average lifetime. This incredible workload can manage higher blood pressures without much difficulty in eras when life expectancy was short. However, as people live longer, it may be important to reduce decades of strain on the heart to prolong its functionality. Aging stiffens all muscles, including the heart. Diastolic heart failure (often referred to as ‘Heart failure with preserved Ejection Fraction’ of ‘HFpEF’) is becoming one of the commonest conditions of the elderly and a major cause for hospitalisation. It arises from ventricular stiffening due to age, hypertension, glycosylation and various other rarer heart conditions. The aging component of this process is unavoidable, but maintaining optimal blood pressure through midlife is achievable and, if successful, should prevent additional left ventricular stiffening attributed to hypertension. By regularly monitoring blood pressure and using effective medication, more people could live longer with healthier hearts.
What is a Normal Blood Pressure?
Answering this is akin to asking, “How long is a piece of string?” Severe hypertension (above 150/90 mmHg) clearly increases even short term health risks, requiring aggressive treatment. However, opinions vary on the ideal lower limit. The latest UK NICE guidelines recommends clinic recordings <140/90 mmHg [1], the ACC/AHA targets are lower 130/80 mmHg [4], however blood pressure fluctuates throughout the day, so what appears suitable in the morning may lead to symptoms of low blood pressure in the afternoon.
Large studies have shown that targeting lower blood pressure in higher risk patients reduces the risk of heart failure and adverse outcomes. For people without diabetes or any kind of heart failure a reading of 120/70 mmHg is associated with a lower future risk than 130/80 mmHg, and certainly much lower than 140/80 mmHg. Clinical trials confirm that aggressively lowering blood pressure below current guideline values reduces heart failure and other complications, even though it can sometimes lead to low blood pressure symptoms [2] . It should be remembered however that the evidence is less strong for lowering diastolic blood pressure below 80 mmHg, indeed some trials showed higher coronary event rates when diastolic blood pressure is lowered below 70 mmHg [3], where, it is postulated , reduced coronary perfusion might occur. An individualised approach to target setting is therefore recommended.
Managing Patient expectations
When discussing mild hypertension with a patient and whether to start or adjust blood pressure medication, most patients, when given a clear choice, tend to prefer the manageable risk of occasional low blood pressure. This can often be controlled by drinking more fluids, being cautious when standing up, or lying down briefly. They usually prefer this over the higher risk of heart failure or stroke in later life. Therefore, it seems wise to treat mild hypertension aggressively.
Beyond Stroke Prevention: The Benefits of Lower Blood Pressure
Hypertension is linked to increased risk of the dreaded stroke, though its impact on preventing coronary disease is comparatively smaller. However there are larger benefits of having lower blood pressure through midlife in preventing arrhythmias and heart failure in later life. For example patients with mild hypertension who are prone to atrial arrhythmias can be managed by reducing blood pressure, rather than use anti-arrhythmic drugs.
For those over 70, or with heart failure the optimum blood pressure to shoot for is more uncertain, as there appears to be higher risk of hospital admission and mortality associated with systolic pressure below 130 mmHg. However without a controlled trial, we cannot be sure whether this is due to overzealous treatment or simply because those heart failure patients with lower blood pressures are sicker.
Summary
My goal is to find a balance that achieves the lowest possible blood pressure to help prevent cardiovascular diseases such as heart failure in old age without debilitating side effects. By understanding the genetic, dietary, and lifestyle factors that affect blood pressure, and by using modern treatments like ACE inhibitors, calcium channel blockers, and spironolactone, I believe we can better support healthier hearts and improve quality of life and longevity.
The Naked Heart is an educational project owned and operated by Dr Edward Leatham. It comprises a series of blog articles, videos and reels distributed on Tiktok, Youtube and Instagram aimed to help educate both patients and healthcare professionals about cardiology related issues.
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