A high blood pressure simulation

How it works

The simulation follows 500 men with untreated high blood pressure for 20 years, showing strokes, heart attacks, and heart failure as they happen. Each man is 55, does not smoke, does not have diabetes, and has a blood pressure of 155/95. The simulation then re-rolls the dice as if each man’s systolic blood pressure (the top number) had been lowered by 18 points with treatment.

This is a Monte Carlo simulation: for each man, we roll dice weighted by likelihood.

Baseline risk. Without treatment, over 20 years, each of these men has a 33% chance of a major cardiovascular event: a stroke, a heart attack, or heart failure. This figure is derived from the Framingham Heart Study’s risk formula. In the simulation, 40% of these events are fatal, either right away or within the next few years.

Treatment. A 2016 analysis that pooled blood pressure trials finds that each 10-point drop in systolic blood pressure lowers the risk of a major cardiovascular event by 20%. An 18-point drop therefore brings the 33% risk down to 22%. Well-controlled treatment typically lowers systolic pressure that much, often with more than one medication. The share of events that are fatal stays the same, so fewer events means fewer deaths.

Caveats. The simulation models one kind of patient. Besides blood pressure, a real person’s risk depends on their age and sex, whether they smoke, and whether they have diabetes or other health conditions. Women of the same age and blood pressure have a lower risk than the men in the simulation. The simulation ends after 20 years, and nobody in it dies of anything else, though in real life some men like these would die of other causes first. It counts only deaths that follow a stroke, heart attack, or heart failure. Treatment also prevents some other deaths, such as sudden cardiac death and death from a ruptured aorta (the body’s main artery), so the simulation understates the benefit of treatment. The simulation does not show side effects of medication, or the effects of diet, exercise, and weight loss, which can lower blood pressure further.