Appalachian Health and Well-Being

1. Genetic Contributions to Health

27 1 Genetic Contributions to Health Melanie F. Myers and Carol S. Baugh Genetic factors are well-recognized contributors to the overall health of populations; however, their contribution to the incidence and prevalence of health conditions in the Appalachian population has not been systematically studied. This dearth of information may be due to the underrecognition of genetic conditions owing to the absence of systematic health surveillance systems in Appalachia; limited access to health care services and, specifically, to genetic specialists; lack of education among health professionals about genetic conditions; and limited investment in social capital, resulting in restricted resources and competing health and other priorities.1, 2 The economic and demographic diversity in Appalachia compounds the difficulty of ascertaining genetic contributions to health in the region, as well as among those who have migrated elsewhere.3, 4 Given the heterogeneity of Appalachia, there is likely to be a substantial amount of genetic diversity. This chapter describes what has been published about the genetic in- fluences on health in Appalachia. It begins with a brief overview of the health of Appalachians, followed by a review of the common inheritance patterns of genetic conditions. The main focus of this chapter is use of the family health history as a health promotion tool to capture shared environmental , behavioral, and genetic risk factors. Two components often included in a family history are ethnic origins and the prevalence of consanguinity—that is, individuals’ relatedness through shared common ancestors. General challenges in assessing the genetic contribution to common chronic diseases are addressed at the end of the chapter, along with a discussion of the need for additional genetic studies and policy actions. 28 Myers and Baugh Health in Appalachia Although there are limited data about genetic contributions to health in Appalachia, inferences can be drawn from information on mortality rates and disease prevalence. Health disparities have been well documented in rural Appalachia and are exacerbated by geographic, historical, and socioeconomic factors.5, 6 As a whole, the Appalachian region experiences higher mortality than the non-Appalachian United States with respect to heart disease, cancer, stroke, chronic obstructive pulmonary disease, and diabetes .3, 7 According to a 2004 Appalachian Regional Commission report,3 high death rates due to heart disease are predominant in the Central and Southern subregions, whereas high death rates due to cancer are predominant in Central Appalachia alone. With the exception of white women aged 35 to 64 years, Appalachians have higher breast cancer death rates than nonAppalachians . Colorectal cancer death rates for white men and women are higher in the Southern subregion. The Appalachian region also has higher lung cancer death rates than elsewhere in the United States. High death rates from stroke are predominant in the Southern subregion, whereas high death rates among whites from chronic obstructive pulmonary disease are predominant in the Central subregion. High death rates due to diabetes are predominant in the Central and Northern Appalachian subregions . It is worth noting that heart disease, stroke, and cancer are all multifactorial conditions. Higher rates of obesity and smoking, lower rates of physical activity, and environmental exposure to coal mining, for example, undoubtedly contribute to the high death rates among Appalachians,3 as do poor socioeconomic conditions such as poverty and the lack of health insurance.5 Although efforts are under way to learn how genetic susceptibility influences the occurrence of common multifactorial diseases, this area of study is still nascent. Inheritance and Genetic Conditions To appreciate how genetics can contribute to health in individuals and populations , a general understanding of genes and chromosomes and the different categories of genetic conditions is essential. Genes, which are made up of DNA (deoxyribonucleic acid), are the basic units of inheritance.8 Each person has two copies of a gene—one inherited from each parent. Genetic Contributions to Health 29 Genes and DNA are further packaged into structures called chromosomes. Like genes, chromosomes come in pairs, with one chromosome in a pair inherited from each parent. Typically, each individual has forty-six chromosomes (twenty-three inherited from each biological parent). The first twenty-two pairs of chromosomes are called the autosomes and look the same in males and females. The sex chromosomes are the twenty-third pair. Females have two copies of the X chromosome, while males have one X and one Y chromosome.8 Mutations are changes in the DNA sequence that makes up a gene. These gene...