The Intergenerational Impact of Genetic and Psychological Factors on Blood Pressure Study (InterGEN)

Abstract

Background Although studies show that genomics and environmental stressors affect blood pressure, few studies have examined their combined effects, especially in African Americans. Objective We present the recruitment methods and psychological measures of the Intergenerational Impact of Genetic and Psychological Factors on Blood Pressure (InterGEN) study, which seeks to investigate the individual and combined effects of genetic (G) and environmental (E) (psychological) stressors on blood pressure in African American, mother-child dyads. Genetic methods are presented elsewhere, but here we present the recruitment methods, psychological measures, and analysis plan for these environmental stressors. Methods This longitudinal study will enroll 250 mother-child dyads (N = 500). Study participation is restricted to women who: (a) are ≥ 21 years of age; (b) self-identify as African American or Black; (c) speak English; (d) do not have an identified mental illness or cognitive impairment; and (e) have a biological child between three to five years old. The primary environmental stressors assessed are parenting stress, perceived racism and discrimination, and maternal mental health. Covariates include age, cigarette smoking (for mothers), and gender (for children). The study outcome variables are systolic and diastolic blood pressure. Analysis The main analytic outcome is genetic-by-environment interaction analyses (G × E), however, main effects (G) and (E) will be individually assessed first. Genetic (G) and interaction analyses (G × E) are described in a companion paper and will include laboratory procedures. Statistical modeling of environmental stressors on blood pressure will be done using descriptive statistics and generalized estimating equation (GEE) models. Implications The methodology presented here includes the study rationale, community engagement and recruitment protocol, psychological variable measurement, and analysis plan for assessing the association of environmental stressors and blood pressure. This study may provide the foundation for other studies and development of interventions to reduce the risk for hypertension, and to propose targeted health promotion programs for this high-risk population.

A Systematic Review of DNA Methylation and Preterm Birth in African American Women

“…Researchers are currently engaged in larger studies with longitudinal study designs and diverse samples that hold promise for increasing our understanding of maternal–fetal epigenomic interactions that lead to PTB. Ongoing studies may also provide opportunities to improve our understanding of how DNAm is associated with PTB specifically in African American women and children (Crusto, Barcelona de Mendoza, Connell, Sun, & Taylor, 2016); Taylor, Wright, Crusto, & Sun, 2016). Another potential limitation is the inclusion of studies that used growth and gestational age as their primary outcome rather than PTB specifically.…”

Novel DNA methylation sites associated with cigarette smoking among African Americans

“…Women must enroll with a biological child (3-5 years old) who lives with her most of the time and can spit to provide saliva sample. More information on the cohort and psychological measures can be found in previous reports [34]. During the baseline study visit, study personnel take clinical measurements of blood pressure, height, and weight and collect saliva for DNA analysis from both mother and child.…”

The Intergenerational Impact of Genetic and Psychological Factors on Blood Pressure (InterGEN) Study

“…We provide detailed description of participant recruitment and environmental and interview data collected for the study in a companion manuscript (Crusto, Barcelona de Mendoza, Connell, Sun, & Taylor, in press). Briefly, we will enroll English-speaking mothers, 21 years of age or older, who self-identify as AA or Black and have no active psychological or cognitive impairment, with one of their children aged 3–5 years.…”

“…Each phenotype and genomic marker will be modeled separately. The general model to be fitted will be as follows: $$Y_i={\beta }_0+{\beta }_1{Z}_i+{\beta }_2{E}_i+{\beta }_3{G}_{1i}+{\beta }_4{G}_{2i}+{\beta }_5{G}_{1i}*E_i+{\beta }_6{G}_{2i}*E_i+e_i$$ where Y i is the BP outcome (e.g., systolic and diastolic BP) for person i, Z i is a vector of adjustment variables, E i is the relevant psychological environmental measures identified by methods described in the companion paper (Crusto et al, in press), and G 1i and G 2i are dummy variables to capture variation in SNP genotypes. SNPs with minor allele frequencies of < 5% will be flagged and related results interpreted with caution due to suboptimal power.…”