Genetic and Environmental Risks for High Blood Pressure Among African American Mothers and Daughters

Cardiovascular (CV) changes that lead to high blood pressure (HBP) have become commonplace in American society, often beginning in childhood. The national trend of obesity has been suggested as a leading cause of HBP (American Heart Association [AHA], 2003; Din-Dzietham, Liu, Bielo, & Shamsa, 2007; Litwin et al., 2007). The percentage of children with body mass indices (BMIs) surpassing the 95th percentile, indicating obesity, has risen steadily over the last 20 years (aCenters for Disease Control and Prevention [CDC], 2007a). Statistically, African American women and girls are more overweight and obese than those of other ethnic groups. From 2003 to 2004, statistical trends among 6–11 years olds indicated that 14% of White and 17% of African American boys and 13.1% of White and 22.8% of African American girls were obese. The adolescent years produced an increase in the percentage of obese children in each group, excluding White girls. For ages 12–19 years, 14.6% of White boys and 12.7% of White girls were obese, while 18.7% of African American boys and 23.6% of African American girls were obese. The trends among adult African American women were even more alarming, with 78% of African American women overweight and 50.8% obese. Clearly, though obesity is a concern for everyone, African American females are disproportionately at risk. The increase in the number of overweight and obese children has been associated with the number of children being diagnosed with essential hypertension (Din-Dzietham et al., 2007). Between 1988 and 2002, the percentage of children with prehypertension rose from 7.7% to 10%, with the percentage of children with hypertension increasing from 2.7% to 3.7%. These percentage increases translate into approximately 410,150 additional children diagnosed with pre or essential hypertension across the nation. These statistics signify an important public health concern as hypertensive children usually become hypertensive adults who often develop CV disease along with additional comorbidities at younger ages. Studies have shown linkages among obesity, insulin resistance, metabolic syndrome, and CV changes that lead to HBP (Barlow & the Expert Committee, 2007; Berenson, Srinivasan, Chen, Li, & Patel, 2006; Din-Dzietham et al., 2007; Litwin et al., 2007). Maternal obesity has been recognized as a contributing factor in developing obesity in childhood (Strauss & Knight, 1999), and metabolic syndrome among parents is associated with a higher incidence of metabolic syndrome in children, especially within the African American population (Meis, Schuster, Gaillard, & Osei, 2006). Findings from the CDC National Health and Nutrition Examination Survey (2007b) maintained that African American women have the highest rate of obesity in the 20–39 age groups. Unlike for Mexican American and White women, this prevalence continues to rise throughout African American women’s lifetime to reach a staggering 61% by the time they reach age 60. The American Heart Association (AHA, 2007; Rosamond et al., 2007) has reported that CV disease is the primary cause of death among African Americans, with nearly 5 out of 10 African Americans developing CV disease. African American women have the highest prevalence of HBP of all demographic groups (AHA, 2007; Nesbitt & Victor, 2004). African Americans also experience a high percentage of HBP-related morbidity at an earlier age (Sile et al., 2007). In 2004, 40.9% of the 31,608 women who died from HBP-related diseases were African American; in contrast, 14.5% were White women (AHA). HBP-related diseases include stroke, heart attack, and other cardiovascular compromise. The purpose of the study described below was to examine the risk factors for development of HBP, or hypertension, in African American women. A secondary purpose was to determine the extent to which genetic precursors for hypertension affect the gene-environment interaction for development of HBP early in life. We hypothesized that both genetics and environmental lifestyle behaviors can contribute to the development of hypertension. The research questions address the following: (a) What is the relationship between genetic polymorphisms and blood pressure (BP) readings in African American mothers and daughters? and (b) What is the interaction effect between genetic polymorphisms and environmental lifestyle behaviors (dietary sodium intake and minutes of physical activity) on BP among African American mothers and daughters?