The majority of people treated for blood pressure (hypertension) have mild hypertension. Mild hypertension is defined as a systolic (upper figure) of 140 to 159 systolic and diastolic (lower figure) of up to 90 to 99 diastolic. It is very common affecting millions of people in the UK. Keep in mind that blood pressure goes up with age so it far less significant in older age groups.
Also blood pressure is often higher when taken in a hospital or at a doctor’s surgery (what is called white coat hypertension), so it is essential to have a series of home reading done (which can be much lower) before making a diagnosis of hypertension.
There is no question that treating severe hypertension dramatically reduces the risk of a stroke but the question is does treating mild hypertension make much difference? The huge MRC trial of mild hypertension involving 17,000 people gave us an answer. It looked at people with a BP with a diastolic between 90 and 110. Did it did reduce strokes? Yes but only marginally. It improved the chance of not having a stroke from 97.4% to 98.6%. Once the maths was done they found it would take 9000 years of treatment to prevent one death. This minor benefit needs to be balanced against the many common side-effects of treatment.
The independent Cochrane Collaboration looked at mild hypertension again (BP of 140-159 systolic, 90-99 diastolic), examining 5 different trials involving 8,919 patients. They found that treatment made no difference to either cardiovascular events (such as heart attacks) or strokes.
A study from UK primary care of 38,286 people between 18 and 74 with BPs between 140/90 and 159/99 and no known risk factors for heart disease found there was no benefit in the treated group in terms of mortality or lower cardiovascular events and some increased adverse effects (syncope, electrolyte disturbances and kidney injury) This was published in October 2018 in JAMA Intern Med.
A study from the Netherlands of those over 85 found those treated for blood pressure had a higher mortality and faster cognitive decline (worsening thinking ability) compared to those who were not treated.
My conclusion, looking at all the evidence, is that if there are no additional risk factors like heart disease or diabetes, then there is no point in treating blood pressure unless levels are consistently above 160/100. There will be no benefit but there will be a potential for harm.