Robert Friis (Chair, Health Sciences Department, California State University, Long Beach ) gives expert video advice on: What is epidemiology?; What is the basic premise of epidemiology?; What are the most common uses of epidemiology? and more...
What is epidemiology?
Epidemiology refers to applying the tools of public health to the population, rather than looking at specific individuals as clinical medicine does. The purpose of epidemiology is to look at the distribution and determinants of diseases and other health problems in the population. This is somewhat different from the focus of the clinician who's looking for signs and symptoms of disease or making diagnoses, but doing it in specific individuals rather than within the population.
What is the basic premise of epidemiology?
The basic premise of epidemiology is that health problems and health issues can be defined according to major characteristic variables, and these are known as person, time, and place variables. For example, many disease entities vary according to geographic location. There are some diseases that we have in some parts of the world, for example, the tropical areas of the world, that we don't have in the United States, that are located in temperate areas. Disease conditions and health problems tend to vary according to racial and ethnic breakdown as well. For example, non-Hispanic white people have certain characteristic forms of morbidity and mortality. And these may not be the same, or expressed to the same extent in other racial groups such as Hispanic whites, African Americans, Asians, or other groups. Another aspect we look at in epidemiology is the variable of time. Health conditions and diseases tend to vary over time. For example, there are seasonal variations in many infectious diseases, an example being influenza. There are long term time trends in diseases. Recently, coronary heart disease has tended to level off or decline. And then, that is being replaced by cancer, which is a fast growing cause of mortality in the United States.
What are the two branches of epidemiology?
One of them is called descriptive epidemiology, and then another one is known as analytic epidemiology. Descriptive epidemiology aims to describe a health condition within the population. For example, how does it vary according to age group, or by geographic location, or by other person variables. Also, place variables and time variables. The purpose of descriptive epidemiology is to try to devise hypotheses about the nature, or ideology, of a disease. For example, if we observe a problem that is relevant to many geographic areas. If we observe in Los Angeles that areas of Los Angeles that have high amounts of traffic have high rates of cancer, then we can already begin to think of some hypotheses about what may be going on, and then conduct further studies to investigate what is happening. In contrast with descriptive epidemiology is analytic epidemiology, which tries to uncover the causes of diseases in populations. There are certain types of study designs that are used in analytic epidemiology. For example, case control studies, cohort studies, and experimental studies. The purpose of this is to take hypotheses that have been identified and then investigate them with respect to ideology, and then try to track down a cause of the disease, such as if it's a chronic disease or an infectious disease, or food borne illness, or whatever.
What are the most common uses of epidemiology?
There are seven identified uses of epidemiology. One of them is to study the history of the health of the population. For example, the types of problems that affect society and humanity have changed over periods of time. If you look at data for the 1900s, you would see that there were certain infectious diseases that predominated at that time. If you compare those with the patterns that we have at present, you would see that many of the infectious diseases have been replaced by chronic diseases of long duration, of long standing. Another use of epidemiology is for diagnosis of the health of the community. In this type of epidemiology, we try to make a picture of the characteristics of the community with respect to its demographic makeup, in terms of particular health problems that exist in the community. From that information we can propose specific plans and programs to intervene in order to optimize the health of the community. Another use is known as studying the working of health services, and this use is sometimes referred to as Operations Research. For example, we want to find out if there are areas of the community or our city or county, our state or whatever geographic subdivision we're looking at, that are lacking in health services or whether there are some that are overlapping. That is also known as Operations Research. Another use of epidemiology is called the study of individual risks. For example, one may have observed the prognosis of cancer patients who are diagnosed with a specific form of cancer, or cancer patients who undergo a certain type of treatment. What is their prognosis over time? How long are they likely to live? The use of epidemiology known as identifying syndromes has to do with identifying characteristic patterns of symptoms and other dimensions that are associated with a specific disease. As an example, the common cold has certain symptoms associated with it or the flu - runny nose, headaches, muscle aches, fever and so forth. This is another use of epidemiology. Completing the clinical picture is still another use of epidemiology, and that has to do with the full manifestations of a disease. Often, clinicians who come into first contact with the disease are only aware of the most acute or dramatic cases of the disease. In reality, there may be other types or other manifestations of the disease. Epidemiology enables us to find out what those are, and the final use of epidemiology is known as the search for causes. An example of this type of use of epidemiology would be to find out what causes chronic diseases such as cancer or heart disease. What causes common infectious diseases that we know about. Sometimes epidemiologists have very little knowledge about the disease when they begin, and as a result of their investigations they're able to more fully uncover the causes for the disease.
What are the main components of epidemiology?
The components of epidemiology include the following: disease determinants - which are the cause or factors, the distribution, and morbidity or mortality. Distribution refers to how the disease occurs in the population, morbidity refers to sickness, and mortality refers to death.
Why is epidemiology considered an interdisciplinary field?
Epidemiology is called an interdisciplinary field meaning that it draws on many different disciplines. An example being statistics and biostatistics, microbiology, toxicology, clinical medicine, even psychology and the behavioral sciences. Epidemiology aims to use the appropriate tools that may exist to investigate and study diseases and disease outbreaks.
What are the scientific foundations of epidemiology?
The specific foundations is discipline that draws on the best things from a lot of different fields. For example, my own background was in psychology. Epidemiology is interested in the psychosocial aspect of disease and process these relating to disease. Demography is certainly important in the description of the population. Microbiology is an aspect of epidemiology. Biostatistics is certainly at the core of epidemiology and is very much a central aspect of epidemiology. Molecular and genetic techniques are now becoming more prominent. In some, epidemiology varies from a large number of disciplines and uses the best tools that it can.
What are the most common methods epidemiologists use to study disease?
One of the common methods that epidemiology uses to study disease is called quantification. Quantification involves translating qualitative information or qualitative impressions into numbers that can be measured. And then, in addition, epidemiology uses a special vocabulary. Some examples of the special vocabulary are morbidity, mortality, incidence, prevalence, rate, risk, and so forth. All of these terms, and vocabulary terms, are characteristic to the discipline of epidemiology.
How does epidemiology approach the study of diseases within a population?
Epidemiology uses an interdisciplinary approach to study the occurrence of diseases in populations. For example, the work of biostatisticians is important in quantifying and measuring the occurrence of disease. The skills of microbiologists are helpful to identify and track down agents of disease. The contributions of demography are certainly important - sociology, psychology and many other disciplines.
What are the most common variables used to evaluate my community's health?
Examples of common demographic variables are the age distribution of the population, the racial and ethnic distribution, socioeconomic status, education, and lifestyle characteristics. Social characteristics relate to social instability, the social support level, affluence, availability of health care facilities and related variables.
Do clinical descriptions of disease differ from epidemiological descriptions of disease?
The clinical description of a disease is quite different from an epidemiologic description. A clinical description involves the use of specific signs and symptoms of a disease. For example, what you might see on your clinical record, such as what your temperature was, or what your height is, or your weight. Essentially, it looks at what your symptoms are. In an epidemiologic description of a disease, we're interested in describing the populations among which the disease is more common, the subsets of the population where it occurs, how it varies by age, gender and other demographic variables.
Which sources of data do epidemiologists draw upon?
Epidemiologists draw from a wide number of data sources, and I can name several examples. For example, one of the most important ones is vital statstics data. This includes data from birth records, death records, surveillance systems mantained by local government that are forwarded to the state level, to the Centers for Disease Control and Prevention. There are data registries that collect data on specific diseases such as cancer, and then there are national and local surveys that are conducted such as the Health Interview Survey and the Health Examination Survey. An example of a local survey conducted in California is the CHIS, or California Health Interview Survey.