[SOUND] [MUSIC] In this lecture, we'll discuss person, place, time, and the population perspective of epidemiology. After you've reviewed this lecture, you should be able to complete these learning objectives. Define descriptive and analytic epidemiology and give examples of each. Characterize two perspectives on disease in populations, the biomedical perspective and the population perspective. And apply the population perspective to an understanding of the global burden of disease. Descriptive epidemiology refers to characteristics of persons such as age, sex, race, and socioeconomic status. Characteristics of place such as country, province, state, city, zip code, or census track. And characteristics of time such as long term trends short term variations by week or day. When we ask what is the distribution or pattern of a disease or health outcome in the population we are talking about descriptive epidemiology. Descriptive Epidemiology deals with the frequency and the distribution of disease or risk factors in populations. Descriptive Epidemiology can be used for hypothesis generation, but Descriptive Epidemiology usually cannot be used to test hypothesis. This graph shows lung bronchus cancer risk by amount of smoking per day. This is an example of looking at a distribution of disease by person. Personal characteristics include age category and smoking history. This map shows the estimated tuberculosis incidence rates in 2010 by country. This graph is an example of examining the distribution of disease by place. This graph is an example of examining the distribution of disease by time. It shows trends in obesity among children and adolescents in the US from 1963 to 2008. Descriptive epidemiology can be used to evaluate trends in disease, health, and risk factors such as smoking or determine if a health status is improving or getting worse. To determine if new diseases are occurring, and provide a factual basis for evaluating public health programs and services. To determine if existing programs are effective, or if new programs should be developed. Descriptive epidemiology can also be used to identify problems to be studied by analytic epidemiology. Analytic epidemiology aims to research and study risk factors and preventive factors for diseases. When we ask the question, what are the underlying causes of this pattern of disease or health outcome and investigate the causes we are using Analytic Epidemiology. Use of a comparison group is a key feature of Analytic Epidemiology. It focuses on the search for causes and effects, or the why and the how, of what causes a health outcome. For example, a study on the causes of obesity would examine dietary differences among two or more comparison groups. Let's now briefly discuss two different perspectives on disease and health. The biomedical perspective and the population perspective. The biomedical perspective focuses on biological factors, such as specific agents that cause disease and their mechanisms. The biomedical perspective focuses on individual risk factors for health outcomes. The biomedical perspective does not include social and environmental factors. Researchers and clinicians observed and or measure the events that occur sequentially in someone's body when they come into contact with a disease agent or exposure. These observations and measurements help us to understand biological mechanisms of disease development, and the transmission of disease. This example shows the mechanism for transmission of the malaria parasite to humans. Information about the environment in which a human is exposed to malaria parasites is not included in this perspective. Biological parameters for example blood pressure, body temperature, lung function, heart rate and laboratory data from blood or tissue samples are the focus of the biomedical perspective. Now, let's look at the population perspective. The population perspective focuses on social, psychological, and environmental factors that are associated with health outcomes. The occurrence of health outcomes, or disease in populations, is impacted by immediate causal agents as well as other factors. For example, the housing conditions in which people live can influence their health. How can researchers determine which specific factors affect the health of a population? One way is to examine things from a population perspective. With the population perspective we look at both proximal, or downstream, and distal or upstream factors. Downstream health factors are micro level factors and include physiological and biological factors such as, genetic makeup, age, ethnicity, gender and immune status. Downstream determinants typically are related to illness and disease. Risk factors that cannot be changed can be used to identify groups of people at increased risk and to develop targeted interventions. Upstream health factors are macro level factors. Such as global forces and government policies. Upstream public health approaches try to prevent health problems at the source, so they don't need to be fixed down the stream. Factors such as community design, education, employment, living and working conditions and poverty are major determinants of health that may be addressed upstream. We can also look at the underlying causes of disease or health outcomes in populations. For example, underlying environmental, economic, social, and cultural factors. Such underlying factors for example, may affect how viruses mutate over time and adapt to their environment. When we talk about the population perspective we are referring to a web of causation where many factors may play a role in disease development. Factors including family support, social networks, global climate, labor conditions, tobacco production or even advertising. Each and everyone of these may all play a part and should be considered when deciding public health interventions. A population health perspective can also focus on health disparities, especially health disparities related to socioeconomic status. All epidemiologic research involves some sort of population. Every population has its own history, culture, and economic and social context. Which influences how and why people are exposed to risk factors. And how people are affected by their exposures. Population research begins by considering the distribution and determinants of health outcomes at a population level. Though population research may also include individual and micro level analysis. And understanding of the historical and social context of health outcomes is important in order to conduct effective research and to design effective interventions. So, how do health problems develop? Health problems can develop in many different ways. For example, infections may enter the body from the outside, such as viruses that cause the common cold, or bacteria that cause strep throat. People may be exposed to toxic chemicals such as lead or arsenic through their environment or job. An individual's genetic may lead to improper growth function, and/or maintenance of their body systems, for example, type one diabetes. In addition, behaviors or acquired risk factors such as smoking, alcohol abuse, inadequate exercise, psychological stress, and poor diet may all contribute to health problems. Other health problems can develop from the result of accidents such as head trauma caused during a car accident or a fall. And social factors such as poverty and lack of education can expose populations to risks such as unsafe drinking water or prevent people from obtaining adequate medical care. Lung cancer is an example of a disease that is well understood. Most cases of lung cancer can be attributed to cigarette smoking. The biomedical mechanism of lung cancer took cigarette smoking is understood. It's well known that carcinogens in tobacco smoke cause disease. But the addictive properties of nicotine make it difficult to quit smoking. However, there is a social context to the disease. Since culture and social factors can influence who smokes and who doesn't smoke. We'll now talk about the social factors involved in lung cancer attributable to cigarette smoking. In the past, smoking was seen as a status symbol, and a sign of leisure or stress reduction. This was enforced in media by showing movie stars smoking in a way that promoted leisure and stress reduction. In addition, smoking was ubiquitous in the workplace until the 1980's. For example, some professors smoked while lecturing and doctors even smoked in exam rooms. There's also the example of a cigarette company in the early 1900's, who changed their packaging and marketing of women's cigarettes to match the color of the year. To try to entice more women to smoke. This was done because smoking was initially seen as a masculine pastime. The women's suffrage movement and the rise of feminism led to more women smoking and more exposure on the job as more women smoked outside of the home. These vintage ads for cigarettes and smoking portray the social context of smoking. It seemed like everyone, everywhere was smoking. Now we will discuss a different disease example, diabetes. The cause of diabetes may have genetic, physiological, psychological, familial, social, economic, cultural, and political aspects. For example, events that occur during fetal development and also maternal factors, may influence whether someone gets diabetes later in life. Genetic factors play a role. Social factors, such as nutritional change to eating higher calorie foods, and higher fat foods, urbanization, immigration and cultural perceptions of what it means to be overweight or obese may have an effect. Economic factors such as changes in the cost and/or availability of food in certain areas may also play a role in the development of diabetes. To summarize what we have learned about the population perspective, we'll now compare it to the mission of public health. The population perspective focuses on describing patterns, identifying underlying causes of health problems, and developing interventions at the population level. In contrast, the mission of public health is to provide conditions that promote health, develop interventions or programs at the community level and to make sure laws and mass media promote health. This concludes our lecture on the population perspective of epidemiology. [MUSIC]
