Understanding Epidemiology: Key Insights for Public Health
School
University of Georgia, Tbilisi**We aren't endorsed by this school
Course
BIOETHICS 157A
Subject
Nursing
Date
Dec 12, 2024
Pages
7
Uploaded by DeanElephantMaster1093
Public Health - Evidence based public healthPpt 6EpidemiologyEpidemiology is an important component of the assessment function of public health. Epidemiologists investigate epidemics of known and unknown diseases by counting the number of cases and identifying how they are distributed by person, place, and time.Using this information, they can often determine a probable cause of a new disease or a reason for an outbreak of a previously controlled disease. This knowledge allows public health workers to institute measures aimed at preventing and controlling the spread of the disease.An early achievement of epidemiology was the recognition in the 19th centurythat cholera was spread by polluted water. John Snow conducted pioneering investigations on cholera epidemics in England and particularly in London in 1854 in which he demonstrated that contaminated water was the key source of the epidemicsIn 1993, similar epidemiologic methods determined that polluted water had caused an outbreak of cryptosporidiosis in Milwaukee.Epidemiology also sheds light on the causes of chronic disease. Formal, long-term studies of heart disease and lung cancer provided the earliest information on the risk factors that contributed to these diseases. The Framingham Study, which has trackedcitizens of Framingham, Massachusetts, for more than six decades, identified high blood pressure, high blood cholesterol, and smoking as risk factors for heart disease.Two epidemiologic studies conducted through the 1950s and 1960s— one onthe smoking habits of British doctors (Richard Doll and Austin Bradford Hill 1951-2001(largest)) and a similar study on a group of 188,000 American men— indicated a clear link between smoking and lung cancer.Epidemiology’s rolein identifying causes of disease leads directly and indirectly to prevention and control. In some cases, regulatory action by a local government is necessary to eliminate disease causing conditions. Sometimes, simply publicizing the results of a study allows people to modify their behavior to avoid risk factors for a disease. To achieve additional improvements in public health, health agencies build on epidemiologic information to develop policy and plan programs aimed at reducing risk and promoting health in the populationEvidence-based public health approach
1. Problem: What is the health problem? 2. Etiology: What is/are the contributory cause(s)? 3. Recommendations: What works to reduce the health impacts? 4. Implementation: How can we get the job done? 5. Evaluation: How well does/do the intervention(s) work in practice?How Can We Describe a Health Problem?Burden of disease - is the occurrence of disability and death due to a disease.In public heath, disability is often called morbidity and death is called mortality.The course of the disease - asks how often the disease occurs, how likely itis to be present currently, and what happens once it occurs.Rates:
The term “rate” is often used to describe any type of measurement that has a numeratorand a denominatorwhere the numerator is a subset of the denominatorIncidence rate= # of new cases of a disease in a year ________________# of people in the at-risk populationuseful starting point when trying to establish the etiology, or cause, of a problem. Prevalence= # of living with a particular disease #of people in the at-risk populationuseful when trying to assess the total impact or burden of a health problem in a population and can help identify the need for services (screening and diagnoses)How Can Understanding the Distribution of Disease Help Us Generate Ideas or Hypotheses About the Cause of Disease?EtiologyGroup associations may suggest ideas or hypotheses about the cause, or etiology, ofa disease.-Person - age, gender, race, behaviors-Place - geographic location (matters in the occurrence of disease)-Time – even decades to generate hypothesesEtiology: How Do We Establish Contributory Cause?The evidence-based public health approach relies on epidemiological research studies to establish a contributory cause.The “cause” is associated with the “effect” at the individual level - lung cancer are more frequently smokers than individuals without lung cancer.The “cause” precedes the “effect” intime - cigarette smoking comes before the development of lung cancerAltering the “cause” alters the “effect” - reducing cigarette smoking reduces lung cancer rates.
These three definitive requirements may be established using three different types of studies, all of which relate potential “causes” to potential “effects” at the individual level1)Case-control Study2)Cohort study3)Randomized control trialCase-control StudyCase-control studies can demonstrate that cigarettes and lung cancer occur together more frequently than would be expected by chance alone.To accomplish this, cases with the disease (lung cancer) are compared to controls without the disease to determine whether the cases and the controls previously were exposed to the potential “cause” (cigarette smoking).These case-control studies established requirement number one—the “cause” is associated with the “effect”at the individual level. They established that cigarettes are a risk factor for lung cancer.Cohort StudyCohort studies are most useful for establishing requirement number two—the “cause” precedes the “effect.”Those with the potential “cause”or risk factor (cigarette smoking) and those without the potential “cause” are followed over time to determine who develops the “effect” (lung cancer)American Cancer Society followed nearly 200,000 individuals over 3 or more years to determine the chances that smokers and nonsmokers would develop lung cancer.Those who smoked regularly at the beginning of the study had a greatly increased chance of developing lung cancer over the course of the study; Randomized Controlled TrialsRandomized controlled trials are most useful for establishing requirement number three—altering the “cause” alters the “effect.”Using a chance process known as randomization individuals are assigned to be exposed or not exposed to the potential “cause” (cigarette smoking).
Individuals with and without the potential “cause” are then followed over time to determine who develops the “effect.” Conducting a randomized controlled trial of cigarettes and lung cancer would require investigators to randomize individuals to smoke cigarettes or not smoke cigarettes and follow them over many years. This illustrates the hardness that can occur in seeking to definitively establish contributory cause.Once there was a strong suspicion that cigarettes might cause lung cancer, randomized controlled trials were not practical or ethical as a method for establishing cigarette smoking as a contributory cause of lung cancer.The strength of the relationshipprobabilityof lung cancer among those who smoke cigarettes compared tothe probability of lung cancer among those who do not smoke cigarettes. To measure the strength of the relationship, we calculate what we call the relative risk.Dose Response RelationshipSmoking more cigarettes is associated with a greater chance of developing lung cancer.One pack<two packs per dayConsistencyA very large number of studies of cigarettes and lung cancer in many countries and among those of nearly every race and socioeconomic group have consistently demonstrated a strong individual association between cigarette smoking and lung cancer.Biological plausibilityCigarette smoke contains a wide range of potentially toxic chemicals that reach the locations in the body where lung cancer occurs.
Despite the convincing evidence that cigarette smoking is a contributory causeof lung cancer, some individuals never smoke and still develop lung cancer. Therefore, cigarettes are not what we call a necessary cause(must) of lung cancer. Others smoke cigarettes all their lives and do not develop lung cancer. Thus, cigarettesare not what we call a sufficient cause (enough)of lung cancer.ImplementationExamining the options for implementation uses a structure we will call the “When-Who-How” approach.“When”- timing in the course of disease in which an intervention occurs. -primary (prevention before disease)-secondary (before symptoms)-tertiary (before disability)“Who” - At whom should we direct the intervention? -clinical care/vulnerable populations/ or everyone in a community or population?“How” - implement interventions?- information (education)-motivation (incentives)-obligation (requirements)EvaluationPublic health problems are rarely completely eliminated with one intervention—there are few magic bullets in this field.studies of cigarette smoking between the mid-1960s, when cigarettes were first declared a causeof lung cancerlate 1990s demonstrated that there was nearly a 50% reduction in cigarette smoking in the United States and that the rates of lung cancer were beginning to fall—at least among males.new understanding of the problem, its etiology, evidence-based recommendations, and options for implementation.The advent of e-cigarettes is again requiring us to utilize the P.E.R.I.E. frameworkto better understand their benefits and harms.
Health statisticsare used for all aspects of public health policy development and evaluation. Uses of such data include health needsidentification, analysisof problems and trends, epidemiologic research, program evaluation, program planning, budget preparation and justification, administrative decision making, and health education.Public health workers monitor the health of a community by collecting and analyzing health data. These data, called health statistics, play a vital role in public health’s assessment function. They are used toidentify special risk groups, to detect new health threats, to plan public health programs and evaluatetheir success, and to prepare government budgets. The NCHS (National Center for Health Statistics) collects its data in two main ways. First, states periodically transmit data they have compiled from local records; vital statistics, including virtually all births and deaths, are routinely collected this way. Second,the NCHS conducts periodic surveys of representative samples of the population, seeking information on certain characteristics such as health status, lifestyle and health-related behavior, onset and diagnosis of illness and disability, and the use of medical care.Vital Statistics- Births and deaths are the most basic, reliable, and complete data collected.Behavioral Risk Factor Surveillance Survey (BRFSS), which is conducted by the federal government in collaboration with the states, also obtains information on health-related behaviors. It asks questions about health; risk factors, including high blood pressure, high blood cholesterol, diabetes, and weight; and health-related behaviors such as diet and physical activity, cigarette smoking, alcohol use, seat belt use, and drinking and driving. In addition, it asks whether people get preventive medical care such as mammograms, Pap smears, colon cancer screening, and immunizations