The link between blood pressure and age

Persistent elevation of high BP can manifest itself by the presence of damage to brain, heart, major blood vessels, kidneys and eye.

Should I treat the high blood pressure?

Beyond the wrinkles and the blemishes that come with advancing years, the invariable march of age will result in changes in the vessels that have served us so faithfully. Just as rubber becomes stiffer and less pliable over time, our arteries will also lose its elasticity and become less distensible. An effect of this is an increase in the upper or systolic blood pressure (SBP) value and labile fluctuation in SBP with varying levels of activities and emotional changes. Hence, it is not uncommon in the elderly to find a blood pressure (BP) of 160/90 at the doctor's clinic, even though the preceding home BP recording showed 130/80 mm Hg.

While many have the impression that an increase in BP is an inevitable consequence of ageing and hence a higher BP is acceptable for those more than 60 years old, the current consensus expert opinion is that BP in the elderly should continue to be maintained at 140/90 mm Hg or less.

'High' blood pressure that is normal

One elevated blood pressure reading does not mean that hypertension or high blood pressure exists. While the pliable and elastic wall of the arteries in a young person allows the arteries to distend and "absorb" the increase pressure that is generated through an increase in heart rate or by stress, the loss in elasticity and stiffening of arteries with ageing means an elevation in the SBP will be more commonly seen with emotional stress, anxiety and physical exercise. Hence, in the elderly, the need to record blood pressures on multiple occasions at rest is necessary before a diagnosis of hypertension can be confirmed.

The elderly are also prone to "white-coat" hypertension, where clinic measurements of BP remain persistently high but the home BP values are normal. Multiple office BP readings are insufficient in such situations and home BP readings provide a more accurate reflection of the blood pressure status.

However, office and home blood pressure measurements may still be elevated in the situation of "pseudo-hypertension", a condition where the SBP is falsely elevated as a result of significant stiffening and hardening of the walls of the arteries. In this situation, the cuff inflation during blood pressure recording may have to be inflated to very high pressures before the artery can be compressed, resulting in a highly elevated SBP value and a normal lower or diastolic blood pressure (DBP) value. This may be more often seen in those who have diabetes mellitus where diffuse hardening of the arterial wall is more commonly seen. Furthermore, smaller arteries are more likely to be affected as compared to larger arteries. Hence, in this situation, it may be better to use an arm BP measuring device rather than a wrist BP measuring device. This condition should be suspected if there are absolutely no symptoms and no evidence of any damage to any organs, despite the BP being persistently high and not responding to medication.

The three situations of labile SBP elevation, "white-coat hypertension" and "pseudo-hypertension" are more prevalent in the elderly and a correct diagnosis is important in avoiding overtreatment.

Impact of high blood pressure

Persistent elevation of high BP can manifest itself by the presence of damage to brain (stroke, bleeding, dementia), heart (chamber enlargement, abnormal heart rhythms), major blood vessels (aneurysm or enlargement of the aorta), kidneys (impairment of function) and eye (degeneration of eyesight). An objective way to assess the effect of persistent hypertension is to evaluate the impact of high BP on the heart. The left-side heart chambers are connected to the aorta, the main arterial channel which supplies blood to the entire body. In persistent poorly controlled hypertension, the thinned walled left upper heart chamber will be enlarged and the muscular left lower chamber will have thickened walls as the heart chamber has to pump harder against a higher BP for the blood to enter the aorta. This can be objectively confirmed by an ultrasound examination of the heart, echocardiography. The absence of these changes on echocardiography in the presence of persistently high BP not responsive to medication and yet not accompanied by symptoms should lead one to suspect "pseudo-hypertension".

How low should the blood pressure be?

In certain situations, a lower blood pressure value is preferred. For those with weak hearts, diabetes mellitus and chronic kidney disease, the general consensus opinion is that the BP should not be more than 130/80 mm Hg. For those with swelling of the aorta, the blood pressure has to be well controlled to be consistently below the target values to reduce the risk of a sudden rupture of the aorta, a condition that carries a high risk of death.

Lower BP may not always be necessarily better. Multiple trials have demonstrated that for the elderly and for those with underlying blockage of the heart arteries, lowering the BP to 130/80 Hg or less is associated with increased incidence of death from heart disease; the so called J-curve effect where the benefits of BP lowering reverse to a detrimental effect when the BP drops below a certain value. Hence, if you are an elderly diabetic, do not be overly enthusiastic in lowering the BP levels excessively, as there is no additional benefit and it may even be detrimental. For octogenarians, as a result of age-related decreased circulation to the organs and a higher risk of a postural drop in BP on standing, the BP should not be lower than 130/80 mm Hg.

Till future trials provide evidence for the "ideal" blood pressure range for the elderly and for those with significant blockage of heart arteries, the prevailing expert opinion recommends lowering BP to values within the range of 130-139/80-85 mmHg.

 

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