The association between systolic blood pressure and cardiovascular disease risk exhibits substantial heterogeneity across studies (I² = 75%), which is partially attenuated by adjustment for age and baseline blood pressure, indicating variability in the strength of this relationship across U.S. populations.

As people age, their arteries become stiffer and less elastic, which raises the baseline pressure in the blood vessels. When blood pressure rises further, the stiffened vessels experience more force with each heartbeat, causing more damage to their inner lining. This damage builds up over time and increases the chance of heart disease. Women tend to have more of this damage at the same blood pressure levels because their arteries stiffen differently with age than men's, and their starting pressure is often lower, so each rise in pressure hits harder.