Definition of Epidemiology

• Epidemiology, which translates to “on or upon”, demos which translates into “the common people” and logy which translates into “study,” is the origin of epidemiology. These words are combined to give the following definition: epidemiology is “the study or the effect of what falls upon the common people.”
• Epidemiology is also a branch of medical science that treats epidemics.
• This definition was created by the London Epidemiological Society. It was established in 1850 to identify the causes and prevent the spread of epidemic diseases such as cholera.
• Many definitions of epidemiology were developed over the past century. Some definitions were originally focused on infectious diseases. Later ones encompass all diseases.
• Our definition of epidemiology is: The study of the distribution of diseases and their determinants in humans and the application of that study to manage health problems. This definition is a mixture of an old one that MacMahon, Pugh and Porta created in 1970 and a newer one that Porta has described in the fifth edition of Dictionary of Epidemiology.
• The term “disease” refers to many health-related events and states, including injuries, deaths, and diseases.

Overview of Epidemiology

• Epidemiology focuses on the patterns of disease and ill health in the population.
• Epidemiology is a combination of elements from clinical, biological and social sciences.
• The foundation of epidemiology is clinical practice.
• Epidemiology is a science that aims to discover the causes of disease variation in order to improve the health of individuals and populations.
• Epidemiology is a science that aims to prevent and control disease in people, guide health policy and planning, as well as improve individual health care.
• Good epidemiological variables must meet the needs of epidemiology.
• Although theories are used in epidemiology, they may not be explicitly stated.

Scope of Epidemiology/Objective of Epidemiology

The objectives of epidemiology are to: 

• Learn the natural progression of disease, from its onset to its resolution.
• Find out the prevalence of disease in a particular population.
• Identify trends and patterns in disease occurrence.
• Identify the root causes of disease.
• Assess the effectiveness of preventative and treatment measures for disease.

Major Areas of Discussion in Epidemiology

The Major Areas of Discussion in Epidemiology are;

1. Population,
2. Disease frequency
3. Disease distribution
4. Disease determinants
5. Disease control.

Population

• Because epidemiologists care more about disease occurrence in groups than individuals, populations are the center of all epidemiologic activities.
• A population is a group of people who share a common characteristic, such as a place of residence, gender or age, or the use of certain medical services.
• People who live in Boston, for example, are part of a defined geographical population.
• It is important to determine the size of a population where disease is prevalent. This is because only by comparing the number of cases with the population can we find the true frequency of disease.
• A census, which is a complete count of the population, is often used to determine the size of the population.
• These data come from a variety of sources, including the decennial Census, which attempts to count every American citizen every 10 years. There are also computerized records that record the number of patients who have used medical facilities.

Disease frequency

• The frequency of a disease refers to the number of cases of a particular disease in a population. Counting is an important activity for epidemiologists. It involves three steps: 1) defining disease; 2) establishing a system to count cases within a population; and 3) determining its size.
• To accurately determine who should be counted, it is important to clearly define diseases. Disease definitions are usually based on a combination or pathological and sign and symptoms, as well as diagnostic test results and physical examinations.
• A case definition of breast carcinoma might include the presence of a lump in the abdomen, and other evidence such as mammographic or pathological evidence.
• Hospital patient lists, death certificates, special reporting system such as registries for cancer and birth defects, as well special surveys are all available resources to identify and count cases of disease.
• The National Health Interview Survey, a federally funded survey that collects data about the health status of the U.S. populace since the 1950s, is an example. Its purpose is “monitoring the health of the United States populace” through the collection of information on a wide range of topics including health indicators, healthcare access and utilization, and health-related behavior.

Disease Distribution 

• The analysis of disease distribution refers to the analysis disease patterns according to the characteristics and place and time. In other words, who is getting the illness, where it is occurring and how it is changing over the time.
• These three characteristics are useful in helping epidemiologists understand the health of a population and form hypotheses about disease determinants. They also help them plan, implement and evaluate public health programs that control and prevent adverse events.

Disease Determinants 

• Factors that cause a person to have a disease or make a difference to their health are called disease determinants. Determinants can be both preventive and causal.
• Individual, social, and environmental determinants are also included. Individual determinants include a person’s genetic makeup and gender, age, immunity, lifestyle, and any existing diseases.
• Breast cancer risk is higher in women who have genetic alterations like BRCA1 or BRCA2, are older, have had benign breast disease in the past, or have been exposed to radiation.
• The environment and social determinants have an external impact on the individual. They can affect a variety of natural, economic, and social events.
• Many communicable diseases are caused by environmental and social factors, such as the presence of infectious agents, the reservoirs where the organism multiplies and the vectors that transport it, poor housing conditions and political instability.
• Epidemiologic research is the generation and testing of hypotheses regarding disease determinants.
• Hypothesis is defined as “a tentative explanation of an observation, phenomenon or scientific problem that can then be tested with further investigation.”
• Hypotheses are a creative process that requires imagination and creativity. It usually involves observations about the distribution and frequency of disease in a population.
• Hypotheses are tested by epidemiologists who make comparisons, often within the context of an epidemiologic study.
• A study’s goal is to collect valid and accurate information about the causes of disease in a population.
• There are many types of epidemiologic research. Each type is just a different way to harvest the data.

Disease Control 

• Epidemiologists control disease through epidemiologic research as previously described and surveillance.
• Surveillance is used to identify and monitor disease incidences that can be controlled.
• The Centers for Disease Control and Prevention gathers data on HIV incidence and AIDS in the United States. The surveillance system collects data about every HIV-infected person, including their demographic characteristics, transmission categories (e.g., male-tomale sexual contact or injection drug use), and the diagnosis date. These surveillance data are vital for formulating and evaluating HIV prevention programs.

Fields of Epidemiology

1. Cancer Epidemiology & Cancer Prevention: This course introduces students to epidemiological research methods and the fundamental concepts and issues related to cancer epidemiology. A wide range of malignancies are covered by research, including breast, colorectal and lung cancers, as well as hematologic, ovarian and endometrial cancers.
2. Cardiovascular Epidemiology: To identify the causes and to recommend preventive measures that can be used to reduce the risk of cardiovascular disease.
3. Clinical Epidemiology: Clinical epidemiology uses the concepts and techniques from statistics and decision analysis to solve clinical problems.
4. Environmental and Occupational Epidemiology are closely related to the concentrations of exposure, epidemiology and risk as well as occupational health in Department of Environmental Health
5. The Epidemiologic Methods program provides training in the application and development of new methods in epidemiologic research. Students will learn how to justify and use classical epidemiologic methods for study design, data analysis, and interpretation of results.
6. Epidemiology and Aging: This includes research methods as well as diseases and conditions that are specific to older people. Local experts include researchers who are involved in the study of the epidemiology and treatment of cognitive decline, Parkinson’s disease (depression), age-related macular disorder, Alzheimer’s disease, Parkinson’s, Parkinson’s, Parkinson’s, depression, frailty osteoporosis, urinary problems, successful aging, as well as other conditions.
7. Genetic Epidemiology & Statistical Genetics: Genetic Epidemiology studies the genetic factors that influence disease outcome and risk. This is done to improve our understanding of disease biology and to inform treatment and prevention strategies.
8. Infectious Disease Epidemiology: Research that focuses on the biological and dynamic aspects of infectious diseases.
9. Neuroepidemiology: Provides training in research methods and epidemiology of neurological disorders.
10. Psychiatric Epidemiology: This course introduces students to the concepts and methods of studying genetic and psychosocial variables related to the incidence, prevalence, and outcome of various types of psychiatric disorders.
11. Nutritional Epidemiology: This area teaches students how to assess the nutritional health of individuals and identify their strengths and weaknesses. This includes advanced training in the nutritional factors of disease and methods for analysis that are specific to research into nutritional epidemiology.
12. Pharmacoepidemiology: Pharmacoepidemiology studies the determinants of both intended and unintended effects of drugs, vaccines, biologics, medical procedures, and medical devices.
13. Reproductive, Perinatal, and Pediatric Epidemiology: The focus of this area is on the determinants and diseases in reproduction, childhood, and adolescent growth.