Population heterogeneity in trajectories of midlife blood pressure

Abstract

Background: We investigated whether there are subgroups with different underlying (latent) trajectories of midlife systolic blood pressure (BP), diastolic BP, and pulse pressure in a UK cohort.

Methods: Data are from 1840 men and 1819 women with BP measured at ages 36, 43, and 53 years. We used unconditional growth mixture models to test for the presence of latent trajectory classes. Extracted classes were described in terms of a number of known lifetime risk factors, and linked to the risk of undiagnosed angina (Rose questionnaire) at age 53 years.

Results: In both sexes for systolic BP, diastolic BP, and pulse pressure, there was a large "normative" class (>90% of the sample) characterized by gentle annual increases (eg, an increase in male systolic BP of 0.9 mm Hg/year [95% confidence interval = 0.9 to 1.0]), with a smaller class for whom the rate of increase was high (eg, an increase in male systolic BP of 3.1 mm Hg/year [2.8 to 3.4]). In women, there was an additional class for whom BP was high at age 36 and remained high. Persons in the "normative" classes were, on average, heavier at birth and taller at age 7 years, had a lower midlife body mass index, and were less likely to be on antihypertensive medication compared with those in other classes. Among those with no diagnosed cardiovascular disease, those in the classes with more strongly increasing systolic BP and pulse pressure were at greatest risk of angina.

Conclusion: Our study suggests that in midlife the majority of the population have a gentle underlying increase in BP, but that there also exists an important subgroup in whom BP increases much more markedly. These classes may be useful for identifying those most at risk for cardiovascular disease.

Figure 1

Median and 10^th and 90^th centiles for observed systolic BP (top 3 solid lines), diastolic BP (middle broken lines) and pulse pressure (bottom 3 dotted lines) in A. men and B. women at ages 36, 43 and 53 years. The bottom line (thick) is the percentage on treatment for hypertension. .

Figure 2

Predicted mean (thick lines) systolic blood pressure (top panel), diastolic blood pressure (middle panel) and pulse pressure (bottom panel) latent class trajectories from GMM models in A. men and B. women. A random selection of observed individual trajectories stratified by most probable class membership are also plotted (thinner lines).