February 4th, 2014
Blood Pressure Trajectory Over 25 Years Predicts Atherosclerosis Risk
Everyone knows that blood pressure is one of the most important measurements of cardiovascular risk. Less well known is that most studies of blood pressure have relied on single or isolated measurements of blood pressure. Few studies have even attempted to examine the significance of blood pressure patterns over a long period of time.
Now, in a paper published in JAMA, researchers present an analysis of data from 3442 adults who participated in the long-term CARDIA study. Study participants were 18-30 years of age at baseline and had multiple blood pressure measurements over the course of the study. After 25 years, they had a CT scan that measured their coronary artery calcium (CAC) score. A CAC score of 100 or greater was considered to be evidence of subclinical atherosclerosis. (Although many doubts have been expressed about the role of the CAC score in contemporary medicine, its use as a marker for subclinical atherosclerosis in a study of this sort is probably not controversial. Because of the young age of the participants at the start of the study, the investigators were unable to study differences in actual cardiovascular events.)
The researchers identified five distinct patterns of blood pressure over time:
- 21.8% of the patients had low blood pressure throughout the study (low-stable). 4% of people in this group had evidence of atherosclerosis on their calcium scan after 25 years.
- 42.3% had moderate blood pressure levels throughout the study (moderate-stable). 7.9% of people in this group had atherosclerosis.
- 12.2% had moderate blood pressure at the start and then had a rapid increase in blood pressure (moderate-increasing). 10.1% of people in this group had atherosclerosis.
- 19.0% had relatively elevated blood pressure levels throughout the study (elevated-stable). 17.4% of people in this group had atherosclerosis.
- 4.8% had high blood pressure throughout the study (elevated- increasing). 25.4% of people in this group had atherosclerosis.
After adjustment for other differences in risk factors between the groups, people in the elevated-increasing group were 3- to 4-times more likely to have atherosclerosis than those in the low-stable group. The investigators note that most of the participants with elevated blood pressures during the study did not meet the definition for actual hypertension but fell within the range of prehypertension (generally defined as a blood pressure between 120/80 mm Hg and 139/89 mm Hg). African-Americans and smokers were more likely to have a rapid increase in blood pressure in middle age.
The authors conclude that their “findings suggest that an individual’s long-term patterns of change in BP starting in early adulthood may provide additional information about his or her risk of development of coronary calcium. In particular, prehypertension at a young age followed by long-term exposure to BP levels in the prehypertension range or higher was strongly associated with a CAC score of 100 HU or greater.”