Epidemiology

NUR 408
October5, 2015

Epidemiology
Epidemiology is the basic principle of public health. According to Hilfinger Messias, McKeown, and Adams (2012, p. 255 ), “Epidemiology has been defined as the study of the occurrence and distribution of health-related states or events in specified populations, including the study of the determinants influencing such states, and the application of this knowledge to control the health problems” (Porta, 2008, p 81). The goal of epidemiology is optimal health for the entire community. It is important to remember that health does not merely mean medical treatment for specific diseases, but also assurance of available services and development and implementation of policies and programs to meet the needs of the population as a whole. Descriptive epidemiology is the study of the “association of health events to person, place, and time” (Stroup, D. & Thacker, S., 2009, p. 262). Analytical epidemiology studies the causes and risk factors of health events. In order to evaluate the health events in a population, both descriptive and analytical epidemiology are important (Stroup, D. & Thacker, S., 2009). Three categories of data sources commonly used in epidemiologic studies including surveillance data, census data, and vital records, data collected for other purposes, and epidemiologic data (Hilfinger Messias, McKeown, and Adams 2012). The epidemiological triangle is composed of three elements of disease, and includes host, agent, and environment. Changes in one element can increase or decrease a person’s risk of the disease (Hilfinger Messuas, McKeown, &Adams, 2012). The purpose of this paper is to describe the epidemiology of children with Down syndrome utilizing the principles of epidemiology, specifically, descriptive epidemiology.

Down syndrome description Down syndrome, also known as Trisomy 21, is a genetic condition in which a child is born with an extra chromosome. A copy of chromosome 21 causes the child to mentally and physically develop differently than a child with the typical 46 chromosomes. There are three types of Down syndrome; Trisomy 21, Translocation Down syndrome, and Mosaic Down syndrome. In Trisomy 21, every cell in the body has a copy of chromosome 21. Trisomy 21 accounts for 95% of the cases of Down syndrome, making it the most prevalent type of the condition. Translocation Down syndrome occurs when a portion or the whole chromosome 21 is attached to another chromosome instead of being a separate chromosome 21. Translocation Down syndrome accounts for 3% of individuals with Down syndrome. Mosaic Down syndrome occurs when some cells of the individual have three copies of chromosome 21 while other cells have two. Mosaic Down syndrome accounts for 2% of the population with the condition, and individuals with Mosaic Down syndrome have fewer of the common features of the condition because some cells have the typical two copies of chromosome 21 ("Centers For Disease Control And Prevention", 2014).
Prevalence
According to "World Health Organization" (2015), “The estimated incidence of Down Syndrome is between 1 in 1,000 to 1 in 1,100 live births worldwide.” In the United States, one in every 691 babies born have Down syndrome ("National Down Syndrome Society", 2012). According to “Centers for Disease Control and Prevention” (2014), “Down syndrome remains the most common chromosomal condition diagnosed in the United States. Each year, about 6,000 babies born in the United States have Down syndrome.” Additionally, according to "Global Down Syndrome Foundation" (2015), “Down syndrome is the most common cause of developmental disabilities.”
Cause and risk factors The cause of the chromosomal aberration leading to Down syndrome is unknown. There are factors which increase the risk of having a child with Down syndrome including advancing maternal age, additional pregnancies after previously having one child with the condition, and passing the genetic form of the disorder to children when either parent is a carrier. ("Mayo Clinic", 2015). Interestingly, according to “National Down Syndrome Society” (2012), “due to higher birth rates in younger women, 80% of children with Down syndrome are born to women under 35 years of age.”
Additional Health problems Children born with Down syndrome have an increased risk of additional health problems.
Fifty percent of children with Down syndrome also have congenital heart defects. Other additional health problems include eye diseases, hearing loss, sleep apnea, ear infections, thyroid disorders, intestinal blockage, anemia, leukemia, and hip dislocation ("Centers For Disease Control and Prevention", 2014). Treatment is available for the additional health problems associated with Down syndrome.
Common physical features Individuals with Down syndrome have common physical features including small ears, short necks, a thick protruding tongue, small hands and feet, a flattened nasal bridge, and a single line across the palm of the hand (“Centers for Disease Control and Prevention, 2012). While physical characteristics are common, individual abilities vary greatly (“Centers for Disease Control and Prevention”, 2012).
Vulnerability
Vulnerable populations have an increased risk of developing health problems and an

increased risk of poor outcomes than the rest of the population (Sebastian, 2012). Historically,

individuals with Down syndrome suffered discrimination and segregation based upon the developmental delays which accompany the condition. In the past, individuals with Down syndrome were institutionalized and denied medical care. However, according to "Global Down Syndrome Foundation" (2015), “Since the 1970s, public schools must, by law, provide a free and appropriate education to children with Down syndrome.” Additionally, due to advocacy and organizational groups, Down syndrome is becoming more accepted in society. Lack of public knowledge continues to be a hurdle in the struggle of inclusion. Furthermore, “Down syndrome is the least funded major genetic condition in the U.S.” (“Global Down Syndrome Foundation”, 2015). The lack of funding means individuals with Down syndrome do not have opportunities to participate in research studies or educational studies. Research is needed to improve all aspects of care related to Down syndrome and to help individuals reach their maximum level of functioning. Without funding, research cannot be conducted.
Primary prevention
According to Hilfinger Messias, McKeown, and Adams (2012, p. 265), “Primary prevention refers to interventions aimed at preventing the occurrence of disease, injury, or disability.” Because the principle cause of Down syndrome is unknown, primary prevention focuses on “avoiding late reproduction, pre-implantation genetic diagnosis (PGD) and folic acid supplementation” (Cuckle, 2005). Further research is necessary in developing primary prevention measures for Down syndrome. In addition, primary prevention includes educating individuals with known risk factors.

Secondary prevention According to Hilfinger Messias, McKeown, and Adams (2012, p. 267), “the aim of secondary prevention is to identify the presence of a disease or condition at an early stage and begin necessary treatment early to increase the likelihood of cure or to prevent further complications.”. In the case of Down syndrome, prenatal screening tests include ultrasounds and maternal blood tests. Prenatal diagnostic tests include amniocentesis, chorionic villus sampling, and percutaneous umbilical blood sampling. Blood tests performed after birth confirm a diagnosis of Down syndrome (“Centers for Disease Control and Prevention”, 2012). Prenatal screening test help prepare parents for the special needs of a child with a disability.
Tertiary prevention According to Hilfinger Messias, McKeown, and Adams (2012, p. 267), “Tertiary prevention includes interventions aimed at disability limitation and rehabilitation from disease, injury, or disability.” Tertiary prevention related to Down syndrome is important in decreasing limitations of the disorder. Tertiary preventative strategies begin with early childhood intervention therapies. The therapies include physical therapy, speech and language therapy, and occupational therapy. Early intervention programs typically begin shortly after birth and continue until the child is at least three years of age. Early interventional programs also assist parents, family members, and society to help individuals with Down syndrome reach their full potential ("National Down Syndrome Society", 2012). Also, support and advocacy groups assist the public in becoming aware of Down syndrome and increase inclusion instead of exclusion. Education is the key to success.

Bias related to Down syndrome Bias related to Down syndrome is mainly due to a lack of understanding of the disorder by the general population. Historical stigma related to the condition, while not as prevalent in today’s society, is still present today. Education through advocacy and support groups helps to decrease the amount of bias related to Down syndrome.
Conclusion
Down syndrome is the most common chromosomal abnormality, yet the least funded in terms of research studies. Three types of the condition lead to varying degrees of developmental and cognitive delays in individuals with the disorder. Because Down syndrome is frequently accompanied by other medical conditions, vulnerability increases. Primary and secondary prevention are difficult due to lack of knowledge related to the causes of the disorder. Tertiary prevention in the form of early intervention therapies help the individual with Down syndrome to reach their full potential. Advocacy, and support groups help the family, and the public to assist individuals with the disorder to reach their dreams and goals. Many resources are available to individuals seeking more knowledge about Down syndrome.

References
Centers for Disease Control and Prevention. (2014). Retrieved from http://www.cdc.gov/ncbddd/birthdefects/DownSyndrome.html
Cuckle, H.S. (2005). Primary prevention of Down's syndrome. International Journal of Medical Sciences, 2(3), 93-99 Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1168873/
Global Down Syndrome Foundation. (2015). Retrieved from http://www.globaldownsyndrome.org/research-medical-care/a-centralized-down-syndrome- registry-and-biobank/
Hilfinger Messias, D.K., McKeown, R.E., & Adams, S.A. (2012). Epidemiology. In M. Stanhope and J. Lancaster (Eds.), Public health nursing: Population-centered health care in the community (pp. 253-284). St. Louis, MO: Mosby Elsevier.
Mayo Clinic. (2015). Retrieved from http://www.mayoclinic.org/diseases-conditions/down- syndrome/basics/risk-factors/con-20020948
National Down Syndrome Society. (2012). Retrieved from http://www.ndss.org/Down- Syndrome/What-Is-Down-Syndrome/
Stroup, D.F., and Thacker, S.B. (2009). Epidemiology and public health data. In C. Keck & S. Crutchfield (Eds.). Principles of public health practice (pp. 234-288). Clifton Park, Delmar : Cengage Learning.
World Health Organization. (2015). Retrieved from http://www.who.int/genomics/public/geneticdiseases/en/index1.html