Hypertension (high blood pressure) is the most frequently seen condition in primary care settings in the United States (James et al., 2014), affecting approximately 78 million adults (Go et al., 2014). African American females have the highest rate of hypertension (49%) compared to African American males (44%), White males (37%) and White females (32%) (Go et al., 2014). The etiology of hypertension is complex and though several biological, environmental and genetic risk factors have been established, few studies have examined the interactive effects that are unique to African American women. Independently, both discrimination and genetics have been associated with high blood pressure (Gravlee, 2009; Taylor, Sun, Hunt, & Kardia, 2010). Few studies, however, have examined how gene-environment interactions that may result in poorer health outcomes for African American women. Our hypothesis was that women with higher levels of racial discrimination will have elevated blood pressures, more deleterious methylation sites on proposed candidate genes, and women with more DNA methylation and higher levels of racial discrimination will have higher blood pressures.
Methods: Baseline data collected between April 2015 and January 2016 from the Intergenerational Impact of Genetic and Psychological Factors on Blood Pressure Study (InterGEN) were utilized for the present study (N = 81). InterGEN is an ongoing prospective cohort study in Connecticut that aims to examine the independent and combined effects of genetic and psychological factors on blood pressure among African American women and their three to five year old children over time. Full study procedures have been described elsewhere (Crusto, Barcelona de Mendoza, Connell, Sun, & Taylor, 2016; Taylor, Wright, Crusto, & Sun, 2016). To be eligible, women were: (a) ≥ 21 years old; (b) self-identified as African American or Black; (c) English speakers; (d) did not have a psychiatric or cognitive disorder; and (e) had a biological child three to five years old. Racial discrimination was measured using three scales: the Race-Related Events Scale (RES), Experiences of Discrimination (EOD) scale and the Major Discrimination (MD) scale. Blood pressure, height, weight, and saliva for DNA analyses were collected at the initial study visit together with the measures of discrimination. Candidate gene analyses was utilized to study the relationship between discrimination and increases in systolic (SBP) and diastolic (DBP) blood pressure. Linear regression models were used to examine main effects of discrimination on blood pressure, controlling for age, education, and antihypertensive medication use. Multivariable linear regression models were also used to test for association between each SNP and the blood pressure phenotypes (i.e., SBP and DBP). Mixed linear models were used to test SNP ´ perceived discrimination interaction effects of SBP and DBP
Results:
A total of 81 women contributed data for the present study. A total of 81 women contributed demographic, clinical and genomic data for analyses. Demographic data indicate (Table 1) that most women were between the ages of 30-39, had a normal BMI, and an annual household income of less than $15,000. Women were most commonly insured by Medicaid (64%), followed by government/ACA insurance (19%) and private insurers (9%). Approximately 15% of women reported ever having received a diagnosis of high blood pressure (n=12) and fewer reported current hypertension medication use (7%, n=6). Most women had higher achieved some college or graduated college (60%). Mean systolic blood pressure was 113.1 mm Hg, and diastolic was 72.3 mm Hg. Overall, women reported relatively few experiences with discrimination based on the three measures (RES, EOD, and MD). A series of linear regression models were then run to examine main effects of experiences of discrimination on systolic and diastolic blood pressure. Models were adjusted for age, education and taking blood pressure medications. Race related events, experiences of discrimination (situational and frequency measures) and major life discrimination were not associated with systolic or diastolic blood pressure in unadjusted or adjusted models. Major life discrimination related to race was associated with a statistically significant increase in systolic blood pressure only (β=4.00, SE 1.8, p=0.030), but this effect was not sustained after adjustment (β=1.73, SE 1.4, p=0.235). Gene and gene-environment analyses will also be presented.
Conclusion:
Preliminary analyses suggest that discrimination may be associated with blood pressure in our sample. Ongoing gene and gene-environment analyses will demonstrate whether an interactive effect is present.