“What’s my blood pressure, Doc?” 

“143/94.”

“That means I have high blood pressure, right? We should start a medication, shouldn’t we?”

Here we have a layer cake of definite maybes. On the bottom layer: the error inherent in measuring blood pressure. 143/94 is just an estimate . If by some superpower we were able to check the same blood pressure on the same person at the same time of day, everything the same, but do it 100,000 times, we might get something a few points lower (138/86, say) or a few points higher. Some of these might be under the magic 140/90 cutoff. Blood pressure itself fluctuates according to time of day, and often – this is the icing on the cake – is not measured in the doctor’s office according to the best evidence. Some have suggested payment incentives to make sure doctors’ offices measure blood pressure correctly.

The next layer is the connection between blood pressure treatment and outcomes that matter to people, accepting for the sake of argument that the person in the dialogue above has, in fact, “mild hypertension” (less than 160 over 100), with no previous heart disease. In a recent meta-analysis from the Cochrane Collaboration, the authors concluded the following:

Antihypertensive drugs used in the treatment of adults (primary prevention) with mild hypertension (systolic BP 140-159 mmHg and/or diastolic BP 90-99 mmHg) have not been shown to reduce mortality or morbidity in [randomized controlled trials]. Treatment caused 9% of patients to discontinue treatment due to adverse effects. More RCTs are needed in this prevalent population to know whether the benefits of treatment exceed the harms.

The final layer is whether, despite the inconclusive studies, medications for blood pressure in this person, as opposed to diet and exercise, would have a net positive as opposed to negative effect.

All that, balanced on the knife-blade of a single visit, with you waiting for your doctor’s answer.

Another slice?