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Blood Pressure: a Fog of Uncertainty

“Knowledge is an unending adventure at the edge of uncertainty.” Jacob Bronowski

When drugs lowering blood pressure came first on the market in the early 60s, many doctors didn’t know how to use them. Guidelines were not available, and most physicians believed that systolic pressure should be measured according to a simple equation: 100 plus a person’s age. Many were convinced that as we get older our blood vessels get stiffer, and the systolic pressure naturally goes up to help push blood through the stiff vessel.

This concept was disproved in 1967 when a groundbreaking study comparing the drugs with a placebo showed that blood pressure medications significantly decrease the risk of heart attacks and strokes and have a great potential to save millions of lives.

Because most clinical trials over the past few decades haven’t been looking at a systolic pressure, the data remains insufficient, and this is the major area of focus today.

The first research on systolic pressure published in 1991 concluded that to prevent heart attacks and strokes, the treatment goal should be a level of pressure below 150. Since then the vast majority of studies were looking to examine the outcomes for higher goals.

This caused major confusion, as although the data was consistent regarding systolic pressure being linked to a lower cardiovascular risk when kept below 120, many doctors were uncertain, if prescribing drugs to reach that level would actually show any benefit. We know that drugs can’t be used selectively. In other words, they always have more effects on the body than the one they are being used for. Lowering pressure down to 120 with drugs is not the same as a naturally low blood pressure of 120.

So, the question remains: how low should blood pressure go?

We still don't know. The guidelines are inconsistent. The National Heart, Lung and Blood Institute suggests that the benefits of treatment are seen when a systolic pressure is below 150 for people over the age of 60. When the results were presented in 2013, a few committee members strongly disagreed and published their own papers independently recommending blood pressure below 140 for people at the highest risk of hypertension. The American Heart Association say it should be under 140. Both institutions don’t take into account individual cardiovascular risks, though.

The European guideline is more precise aiming for a systolic pressure below 150 except older adults, and they recommend measuring a risk score for heart disease when deciding how low that number should be.

Many epidemiological studies suggest that adults with a systolic pressure 120 or lower have been at the lowest risk of having heart attacks and strokes.

Probably one of the weakest points of the guidelines is that they are looking at only blood pressure as though it was a problem isolated from other important factors like daily lifestyle choices or the level of blood cholesterol. Some people are at higher risk than others even though they have the same blood pressure, yet they are supposed to be treated the same way aiming for the same pressure target. That’s confusing.

Reducing high blood pressure is often possible with modifying food choices and encouraging modest exercise like walking. Adding more drugs to meet the target of 120 may not be the best move if the lifestyle remains the same. In fact, the side effects may outweigh any benefit. Older people are particularly vulnerable as many have at least one coexisting chronic condition that may cause drug interaction or lead to dizziness and falls.

Despite years of research, we still don’t know how low blood pressure should go and how aggressive the treatment should be.

The results from one of the largest clinical trials to date, called Sprint, may bring more clarity. The research was expected to be presented in 2017, but it has already ended as the data is conclusive enough to be published. The study was following more than 9,000 people over the age of 50 with high blood pressure and high risk of heart disease, looking at whether lowering a systolic pressure below 120 (the lowest level ever suggested) or below 140 may have a bigger impact on decreasing the risk of heart attacks, strokes, kidney problems and dementia. The full data will be published within the next few months.

In this fog of uncertainty one thing remains valid. Making more conscious choices, following the Mediterranean diet and walking as often as possible is likely to improve our health more than any drug alone could ever do.

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