What is Epidemiology? Introducing the Research and How to Use Data


We have one of the largest scale and highest quality medical databases in Japan, and it is mainly used for epidemiology.

Many people have seen or heard of the word “epidemiology” through media, but not many have a basic knowledge of what it is and what its purpose is.

In this column, we have summarized knowledge and information on epidemiology such as its overview, methods of epidemiological research, and data utilization.

Epidemiology is the Study of the Mechanism of Getting a Disease

What is Epidemiology?

Epidemiology is the study of the mechanism of getting disease based on the causes and prevalence of diseases that occur in human populations.

Epi means “on top of,” demos means “people,” and logos means “study,” meaning that Epidemiology is a study of observing and analyzing phenomena that are happening or about to happen upon people that may be linked to the onset of a pathology.

Epidemiology, as the name implies, focuses on populations rather than individuals, and the actual survey and research involves clarifying the definition of the population, the attributes of the study target such as age, grade, and gender, and then examining the frequency and distribution of events.

The Purpose of Epidemiology

The purpose of epidemiology is to identify and prevent the factors responsible for the occurrence of diseases or health abnormalities in a society.

We seek to identify the causal relationship between disease and risk factors, as well as the possibility of reducing morbidity by breaking the causal relationship.

One of the important implications of epidemiology is that the data obtained from epidemiology provide useful theories and methods for research and practice of preventive medicine.

Epidemiology has made various achievements in its long history, including the elucidation of the mode of cholera transmission in 1854, the elucidation of the cause of beriberi, and the elucidation of the causal relationship between smoking and lung cancer, to list a few.

Overview of “Pharmacoepidemiology” and How it Differs from Epidemiology

One of the study that is often confused with epidemiology is “pharmacoepidemiology.”

Pharmacoepidemiology is the study of the drug use in human populations and its effects and impacts.

The term “drug use in human populations” here means the use of pharmaceuticals in medical settings, and pharmacoepidemiology is mainly regarded as a study of the efficacy, safety, and economics of prescription drugs.

The origins of pharmacoepidemiology are thought to lie in the post-World War II era, when new medicines were developed one after another.

The creation of new medicines has increased treatment options, but it has also caused problems such as aplastic anemia.

So, in 1952, the American Medical Association and the U.S. Food and Drug Administration (FDA) decided to require all doctors in the United States to report cases.

This marked as a starting point of pharmacoepidemiology; researches and studies are being conducted day-by-day as a means of elucidating the causal relationship between adverse events that occur in the human population and the use of drugs so that people can use drugs appropriately.

Difference from Epidemiology

Epidemiology and pharmacoepidemiology are both studies of the causal relationship between the occurrence of adverse events in human populations and risk factors, but there is a major difference in the scope of the studies.

In epidemiology, the object of study is “the distribution and determinant factors of health-related conditions and events in a population,” which can range from diseases, causes of death, behavior, healthy condition, response to health-improvement measures, to the use of health care services.

On the other hand, pharmacoepidemiology aims to elucidate the causal relationship between adverse events that occur when using drugs and its risk factors, and the scope of research is much narrower than epidemiology.

Conversely, pharmacoepidemiology is one of the fields that developed from epidemiology and is classified as “epidemiology” in a broad sense.

Methods of Epidemiological Studies

There are three main types of epidemiological study methods, which are “descriptive epidemiology,” “analytical epidemiology,” and “interventional epidemiology.”

Now, we would like to explain the characteristics of each method here.

1. Descriptive Epidemiology

Descriptive epidemiology is the study of observing and describing the characteristics of diseases in human populations.

“Characteristics of diseases” refer to the frequency of occurrence, distribution, and related information, and these characteristics need to be observed and described in detail by person, place, and time.

The “person” category includes factors such as gender, age, race, as well as genetics and family history, and descriptive epidemiology can elucidate risks such as “high morbidity in men” and “strong genetic element.”

For “place,” in addition to international comparisons, observations and descriptions will be made for a narrower area, such as by region, prefecture, or municipality within Japan.

Since there are differences in dietary habits, lifestyles, climate, etc., not only between Japan and other countries, but also within the same country, descriptive epidemiology can be used to identify risks by location, such as “Japanese men have a higher incidence of cerebrovascular disease than OECD countries [*1]” or “Tokyo has the highest incidence of breast cancer in Japan [*2].”

And in “time,” the characteristics of diseases in various time frames, such as annual, cyclic, and seasonal changes, are observed and described.

For example, the incidence of colorectal cancer has been increasing steadily since the 1970s in Japan [*3].
It is thought that this may be due to the westernization of dietary habits.

Therefore, if we observe and describe the frequency and distribution of disease incidence and related information by person, place, and time, we can make hypotheses about risk generating factors from the results.

[*1] 日本疫学会「記述疫学」The Japan Epidemiological Association (JEA)

[*2] 政府統計の総合窓口「全国がん登録 / 全国がん登録罹患数・率 都道府県一覧 罹患数・率」Portal Site of Official Statistics of Japan

東京都福祉保健局「がんの罹患率」Bureau of Social Welfare and Public Health, Tokyo Metropolitan Government

[*3] 厚生労働省「大腸がん罹患率の推移」Ministry of Health, Labour and Welfare

2. Analytical Epidemiology

Analytical epidemiology is the study of the statistical relationship between hypothetical factors obtained from descriptive epidemiology and diseases, and the estimation of causal relationships.

Descriptive epidemiology is research that clarifies the “Who,” “Where,” “When,” and “What,” while analytical epidemiology pursues the “Why” and tests hypotheses derived from the four “W’s.”

The types of analytical epidemiology are classified into the following four categories:

  1. Case-control study:
    A method to investigate the cause of a disease retrospectively.
  2. Cohort study:
    A method of following populations with and without a hypothesized factor and comparing morbidity or mortality.
  3. Cross-sectional study:
    A method of simultaneously investigating the presence or absence of a disease or health disorder and the possession of a factor in a given population at a given point in time.
  4. Ecological study:
    A method that examines the relationship between factors and diseases in different countries and regions by analyzing not individuals but groups such as regions, countries, prefectures, and municipalities.

Each of these four methods has significant differences in the time relationship between diseases and factors, risk assessment methods, research institutions, and number of subjects.

Therefore, in analytical epidemiology, multiple types of surveys are used together to test hypotheses from different perspectives.

Interventional Epidemiology

Interventional epidemiology is a research method that conducts interventions such as removal or application of risk factors and protective factors, which those causal relationship with disease has been deduced by analytical epidemiology.

The goal is to observe the impact of interventions on human populations for a period of time to see if they are effective in preventing disease and improving prognosis.

There are several types of interventional epidemiology methods, but the one known to be the most standard and effective is the “randomized assignment trial,” also known as “randomized controlled trial.”

It compares two groups of subjects; one with intervention (intervention group) and one without intervention (non-intervention group).

For example, we can verify the effect of the intervention by asking the intervention group to practice the new health method while the non-intervention group practices the conventional health method and comparing the results.

In contrast to interventional epidemiology, which intervenes in the target population, descriptive and analytical epidemiology which do not intervene in the target are also called “observational epidemiology.”

Utilization of Epidemiological study Data

In order to conduct observational epidemiology such as descriptive epidemiology and analytical epidemiology, a vast amount of data is required.

Here, we would like to introduce the main data used for epidemiological studies and how to utilize each of them.

Health Claims Data

A health claim is a statement of medical fees prepared by a medical institution to bill an insurer for medical treatment provided to a patient (health insurance treatment).

In addition to the date and time of medical treatment, the patient’s name, gender, and age, a health claim contains information on the medical institution where the treatment was received, injury and illness information, drug information, medical procedure, material information, and so on.

By reviewing health claims, it is possible to find out when, to who, and where the medical treatment was performed, what kind of injury or disease was diagnosed as a result of the examination, and what kind of medical treatment the patient received.

It is used for descriptive epidemiology and analytical epidemiology studies because of its richness in both the amount of data and the number of items listed.

Pharmacy Claims Data

A pharmacy claim is an invoice for dispensing fees that provides details of medications prescribed by the dispensing pharmacy and its costs.

In addition to the patient’s name, insurer number, and the name of the medical institution where the patient received treatment, the dispensing claim contains information on the name, specifications, dosage, dosage form, and usage of the prescribed medication. This makes it possible to find out who was prescribed what, when, and where.

It is particularly useful for pharmacoepidemiological research, and it is used for survey of the actual use of drugs and for follow-up survey on patients receiving medication.

Insurance Claim Data

Since Japan has a universal health care insurance system, patients only have to pay a maximum of 30% of the total cost at the reception, and the remaining 70% is borne by the insurers who operate health insurance associations.

The insurance claim is created to bill the insurer for this 70%, and is submitted to the Health Insurance Claims Review & Reimbursement Services or the National Health Insurance Organization’s examination and payment agency.

General claims are managed on a per medical institution basis, so if patients are transferred during treatment processes, it is impossible to track them any further. However, with insurance claims, the actual status of a patient’s medical treatment can be tracked as long as the patient does not withdraw from the health insurance plan he or she is taking out.

For this reason, insurance claim data is often used in surveys and research to track a specific patient over a long period of time.

Epidemiology is an Essential Study to Protect People’s Healthy Lives

Epidemiology is a study that aims to identify the frequency and distribution of adverse events that affect human health, as well as their risk factors, in order to seek effective countermeasures.

By conducting epidemiological studies, it is possible to identify the causes of diseases and to find more effective prevention and treatment methods.

Epidemiology is classified into three categories: Descriptive epidemiology and analytical epidemiology which observe events, and intervention epidemiology which intervenes with subjects. In order to conduct descriptive epidemiology and analytical epidemiology which are known as observational epidemiology, a vast amount of data is required.

Epidemiological research is sorted and proceeds in the order of descriptive epidemiology, analytical epidemiology, and interventional epidemiology. Thus, if enough data cannot be obtained at observational epidemiology step, the quality of the epidemiological research will decline.

We have one of the largest medical databases in Japan that can be applied to epidemiological and pharmacoepidemiological studies, and our unique know-how in utilizing medical big data enables advanced data analysis.

If you consider using medical big data for your business, please feel free to contact us.

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