Blood pressure (BP) reactivity to orthostatic tilt may be predictive of cardiovascular disease. However, the genetic and environmental influences on BP reactivity to tilt have not been well examined. Identifying different influences on BP at rest and BP during tilt is complicated by the intercorrelation among multiple measurements. In this study, we use principal components analysis (PCA) to reduce multivariate BP data into components that are orthogonal. The objective of this study is to characterize and examine the genetic architecture of BP at rest and during head-up tilt (HUT). Specifically, we estimate the heritability of individual BP measures and three principal components (PC) derived from multiple BP measurements during HUT. Additionally, we estimate covariate effects on these traits. The study sample consisted of 444 individuals, distributed across four large families. HUT consisted of 70° head-up table tilting while strapped to a tilt table. BP reactivity (ΔBP) was defined as BP during HUT minus BP while supine. Three PC extracted from the PCA were interpreted as "general BP" (PC1), "pulse pressure" (PC2) and "BP reactivity" (PC3). Variance components methods were used to estimate the heritabilities of resting BP, HUT BP, ΔBP, as well as the three BP PC. Significant (P<0.05) heritabilities were found for all BP measurements, except for systolic ΔBP at 1 and 3min, and diastolic ΔBP at 2min. Significant genetic effects were also found for the three PC. Each of these orthogonal components is significantly influenced by somewhat different sets of covariates.
Bibliographical noteFunding Information:
This work was supported by NIH/NHLBI Grants (R01-HL69995, R01-HL070167) and an American Heart Association Ohio Valley Affiliate Postdoctoral Fellowship Grant (0325371B) to ACC.
- Blood pressure
- Cardiovascular reactivity
- Genetic epidemiology
- Orthostatic tilt
- Postural change
- Principal components analysis