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Transcript
Chapter 10 Special Epidemiologic Applications Learning Objectives • Distinguish between molecular and genetic epidemiology • Define the term environmental epidemiology • Describe two applications of occupational epidemiology • State a role for epidemiology in the primary prevention of unintentional injuries and violence Introduction • Scientists utilize epidemiologic methods and concepts with respect to a wide range of health-related and other phenomena including: – Genetically associated diseases – Environmental health – Unintentional injuries – Screen-based media use – Sewage epidemiology Molecular and Genetic Epidemiology • Traditionally, epidemiologic research uncovers associations between exposures and health outcomes, often without fully developing an explanation for the observed associations. – Molecular and genetic methods have increased the ability of scientists to expand the knowledge base of disease causality. Human Genome Project (HGP) • Jointly coordinated by the U.S. Department of Energy and the National Institutes of Health – Completed in 2003 – One goal was to identify all of the genes in human DNA. – HGP will provide valuable information for epidemiologic research • Example: Studying genetic and environmental interactions Molecular Epidemiology • A subfield of epidemiology that uses molecular markers in addition to genes to establish exposure-disease relationships Genetic Marker • “The term genetic marker is used…in reference to susceptibility genes.” • When these genes are present, the person may have increased susceptibility to specific exposures. • An example is the linkage between the gene CYP2D6 and susceptibility to the effects of exposure to benzo-a-pyene, a hazardous chemical. Genetic Epidemiology • The field of genetic epidemiology has a narrower focus than molecular epidemiology. • It is concerned with “…the identification of inherited factors that influence disease, and how variation in the genetic material interacts with environmental factors to increase (or decrease) risk of disease.” Genetic Epidemiology (cont.) • Examples of conditions that are known or believed to have a genetic basis are: – Hemophilia – Tay-Sachs disease – Sickle cell disease – BRCA1 and BRCA2 genes – Down Syndrome – Congenital malformations Sex-Linked Disorder • Hemophilia (bleeding disorder) is caused by an abnormal gene on an X chromosome. – Affected persons are almost always males. – Males inherit the trait from their mothers who are carriers. – Females can be carriers of the abnormal gene, which can be inherited from their affected fathers. Autosomal Recessive • Denotes those diseases for which two copies of an altered gene are required to increase risk of the disease • Examples: Tay-Sachs disease, sickle cell disease Autosomal Dominant • Refers to a situation in which only a single copy of an altered gene located on a nonsex chromosome is sufficient to cause an increased risk of disease. Chromosomal Abnormalities • Example: Down syndrome – Associated with the presence of an extra twentyfirst chromosome Source: Reprinted from Centers for Disease Control and Prevention. Down syndrome prevalence at birth—United States, 1983-1990. MMWR. 1994;43:619 Congenital Malformations • Congenital malformations are defects present at birth. • They include structural birth defects (defined on next slide) and those that are produced by chromosomal abnormalities. Major Structural Birth Defects 1) “…result from a malformation, deformation, or disruption in one or more parts of the body; 2) are present at birth; and 3) have a serious, adverse effect on health, development, or functional ability.” A photograph of a child with cleft feet, or “lobster claw” feet Source: Reprinted from Centers for Disease Control and Prevention. Public Health Image Library, ID# 2631. Available at: http://phil.cdc.gov/phil/details.asp. Accessed July 21, 2008. Environmental Epidemiology • Refers to the study of diseases and conditions (occurring in the population) that are linked to environmental factors. Environmental Epidemiology (cont.) • Representative topics: – Air pollution – Global warming – Toxic chemicals – Heavy metals – Nuclear Facilities Air Pollution • Epidemiologic research has examined a number of adverse health outcomes as possible consequences of exposure to air pollution: – Mortality, coronary heart disease, chronic obstructive pulmonary disease, asthma, and lung cancer Extreme Air Pollution Episodes • Severe, deadly inversion layer in Donora, Pennsylvania (1948) • Killer pea-souper fog, London, England (1952) Global Warming • Global warming refers to the gradual increase in the earth’s temperature over time. • Historical data indicate that the earth’s temperature has warmed approximately 0.6 degrees Celsius since the end of the nineteenth century and about 0.4 degrees Celsius within the past 25 years. Factors Contributing to Global Warming • Use of fossil fuels such as coal and petroleumbased fuels that release greenhouse gases – Carbon dioxide, methane, chlorofluorocarbons, and nitrous oxide • Widespread deforestation in many parts of the world, particularly the Brazilian Amazon jungle Potential Impacts of Global Warming • Global warming linked to: – Northward movement of disease-carrying arthropods (e.g., mosquitoes) – Melting glaciers – Extreme climatic conditions such as heat waves Toxic Chemicals • Chemicals and pesticides are used extensively in industry, at home, and in agriculture. – DDT • Use discontinued because of possible adverse animal and human health effects, e.g., damage to bird species. – Dioxins • Possible disrupters of immune, endocrine, reproductive, and nervous systems – Polychlorinated biphenyls (PCBs) • Dioxin-like chemicals designated as probable human carcinogens Heavy Metals • Industrial sites, metal smelters, some mining operations, and coal-fired power plants can release heavy metals into the environment. – Endanger the health of people who live nearby and employees – Examples: lead and mercury Lead • Lead exposure is associated with serious central nervous system effects and other adverse health consequences, even when ingested at low levels. – Formerly an additive in paints and motor vehicle fuels – Found in automobile batteries and solder used in electronics Mercury • A highly toxic metal that is a particular hazard to the unborn children of pregnant women • Released into the environment as a by-product of industrial processes. – Certain types of fish are believed to contain unhealthful mercury levels. Nuclear Facilities • Include weapons production plants, test sites, and nuclear power plants – Potential sources for exposure of the population to ionizing radiation • Example: Accident in Chernobyl, Ukraine (April 26, 1986) –Nearby population and the residents of many European countries exposed to radiation –Caused an increase in thyroid cancer among persons who were exposed as children Epidemiology and Occupational Health • Occupational epidemiology focuses on adverse health outcomes associated with the work environment. Epidemiology and Occupational Health (cont.) • Potential hazards encountered at work include: – High noise levels – Fumes and dusts – Toxic chemicals – Biohazards – Stress • Exposure levels among employees are often much higher than in the general population. Unintentional Injuries • Injury epidemiology studies the distribution and determinants of injuries (intentional and unintentional) in the population. • This term is preferred to “accident,” the use of which should be avoided. Unintentional Injuries (cont.) • Fifth most frequent cause of mortality in the U.S. (2005) • Many are highly preventable. • Leading causes of injury death (Figure 10-7) are: – Motor-vehicle traffic deaths – Firearm deaths – poisonings Unintentional Injuries (cont.) • The highest death rates from injuries among children and young adults occur during the first five years of life. • Sports-related children’s injuries include traumatic brain injuries. • Traumatic injuries (e.g., ankle injuries) sometimes occur during participation in collegiate sports. • Falls are the leading cause of fatal and nonfatal injuries for persons aged 65 years and older. Other Applications of Epidemiology • Sewage Epidemiology • Descriptive Epidemiology of Screen-Based Media Use • Physical Dating Violence • Forensic Epidemiology Sewage Epidemiology • Refers to monitoring levels of excreted drugs in the sewer system in order to assess the level of illicit drug use in the community. – Research conducted in Milan, Italy; Lugano, Switzerland; and London, England found that cocaine consumption rose in Milan on weekends and heroin consumption varied among the three cities. Descriptive Epidemiology of Screen-Based Media Use • Marshal et al. conducted a systematic review in order to: – “…(i) estimate the prevalence and dose of television (TV) viewing, video game playing and computer use, and – (ii) assess age-related and (iii) secular trends in TV viewing among youth (≤ 18 yr).” • Researchers found that young people watched TV for an average of 1.8 to 2.8 hours per day. The authors concluded that media-based inactivity did not contribute greatly to youth sedentariness. Physical Dating Violence • “Dating violence is defined as physical, sexual, or psychological violence within a dating relationship.” • Youth Risk Behavior Surveillance System – “…measures the prevalence of health risk behaviors among high school students…” – The overall prevalence of dating violence was 8.9% and was similar for both males and females. Forensic Epidemiology • “The use of epidemiological reasoning, knowledge, and methods in the investigation of public health problems that may have been caused by or associated with intentional and/or criminal acts.” • One of the stimuli for the development of this specialization was the 2001 bioterrorism attack (distribution of anthrax bacteria through the postal system) in the U.S. Conclusion • Additional uses of epidemiology covered in this chapter were taken from the fields of: – Molecular and genetic epidemiology – Environmental health – Injury epidemiology • The number and range of applications of epidemiology are likely to increase in the future as are opportunities for research and employment.