Genetic and BMI Risks for Predicting Blood Pressure in Three Generations of West African Dogon Women

The study of genetic and body mass index (BMI) risks of increased blood pressure (BP) among African women is important for increasing our understanding of the factors underlying the development of hypertension in women of African descent. Statistically, African American women are more likely to be overweight than those of other ethnic groups (Centers for Disease Control and Prevention [CDC], 2007a), possessing the highest obesity rate among 20- to 30-year-old women (CDC, 2007b). This finding is particularly alarming considering obesity as a leading cause of high BP (Rosamond et al., 2007). Lifestyle behaviors, such as consumption of high-fat foods, a noted trend in minority and poor populations, are risk factors for obesity and related hypertension (Boutin-Foster, Ogedegbe, Ravenell, Robbins, & Charlson, 2007; Douglas et al., 2003). According to the American Heart Association, African American women have the greatest prevalence of hypertension at 44%, while Caucasians have a prevalence rate of 28.1% overall (Roger et al., 2011). Many African Americans are descendants of slaves brought to the Americas from West Africa during the transatlantic slave trade from 16th to 19th centuries. Among the 10–12 million enslaved Africans who arrived during this period, an estimated 39% came from West Central Africa, including the area now known as Mali (Lovejoy, 2000). The later and larger second Atlantic system of slave trade involved the distribution of Africans to Brazil, Caribbean colonies, and North America. Through this system, slaves from West Africa, the region specific to the present study, were transplanted to the American South (Frey, 2004). Members of the Dogon tribes were among those captured for the West African slave trade (Burnside & Robotham, 1997; Lovejoy, 2000). As late as 1900, nearly 90% of African Americans resided in former slave-holding states (Carney, 1998). Yet, during the Great Migration between 1915 and 1930, many African American slave descendants relocated to industrialized northern cities for better economic and employment opportunities. From 1910 to 1929, Detroit’s Black population increased from 6,000 to 120,000, making Detroit a major northern metropolitan migration destination of Southern Blacks (Gibson, 1998). Today, African Americans comprise the majority of Detroit’s population. Taylor, Maddox, and Wu (2009) conducted a cross-sectional study examining BMI, physical activity, sodium intake, and DNA samples among African American women in urban Detroit to determine associations with high BP. Investigators selected genes to represent biological pathways or positional candidate genes from systems known to be associated with hypertension and previously linked to hypertension (see Table 1). Of the four single nucleotide polymorphisms (SNPs) on the sodium bicarbonate cotransporter gene (SLC4A5), investigators found three to be significantly related to BP in the Detroit sample (rs8179526, rs10177833, and rs6731545). Given the clear, positive genetic, and lifestyle (marginal physical activity and poor dietary habits) interaction effects on BP among that sample, our purpose in the present study was to replicate the genetics piece of that previous study among a sample of West African women in the rural setting of Dogon villages in Sangha, Mali. We have found no published studies that have explored the main and interaction effects of genetic and environmental factors on hypertension development in West African Dogon women. By examining these genetic factors among these two samples of women, we hope to determine if markers for hypertension differ among women with similar heritage but very different lifestyle and environmental factors. Table 1 Single Nucleotide Polymorphisms (SNPs) With a Demonstrated Association With Blood Pressure in African Americans Diet and exercise differ markedly between urban Detroit women and West African Dogon women. Frequent fast-food consumption and lack of physical exercise (Taylor, Maddox, & Wu, 2009) are quite common in Detroit, while processed high-fat foods are nearly nonexistent among the Dogon. The Dogon maintain an agricultural mode of subsistence, cultivating pearl millet, sorghum, and rice, as well as onions, tobacco, peanuts, and other vegetables. The Dogon also raise sheep, goats, and chickens in the region’s villages for sustenance and industry. Women perform the majority of labor in both agricultural endeavors and home maintenance, ensuring that they perform strenuous exercise daily (Strassmann, 1997). In their study of undernutrition in the Dogon region, Schemann et al. (2002) reported that approximately 12.8% of the children were emaciated. Assuming that child weight is a marker for communal nutritional status, some measure of undernutrition probably is present in women of all ages. Because women of the Dogon region have lower body fat ratios and get considerably more physical exercise than urban African American women, it may be that lifestyle factors such as BMI, diet, and physical activity play less of a role in the development of hypertension in the Dogon women. Thus, findings of genetic associations for hypertension among this West African population would help to shed light on the impact heredity and the environment play in hypertension health disparities in Africa and the United States.