What is epidemiology?

Epidemiology is an area of scientific study which thoroughly examines diseases. Epidemiologists seek to identify the patterns in which a particular disease occurs within the population, by utilising tools such as incidence and prevalence rates, death rates, and risk calculations. In doing this, they are able to establish which diseases pose major and minor health threats to the public, allowing them to advise and shape future public policies and interventions to reduce such diseases.

In order to implement such interventions, epidemiologists also study factors which are associated with the incidence of diseases. For example they may look at lifestyle, genetic or environmental influences in order to identify risk factors for disease. The application of this information enables action to be taken in order to reverse serious health threats within the population. Research can also be used to identify which diseases may become epidemics, by examining their changing rates and fluctuations.

After a disease is identified as posing a major health threats, epidemiologists try to assess the influence of risk factors that are associated with the disease. In health research, it is difficult to establish direct causes of disease. This is because, in order to do so, researchers would need, to expose a participant to a proposed risk factor, such as a malaria infected mosquito, and then examine the effects this has upon the body. Evidently, this type of study is likely to cause harm to the participant and so, would be an unethical research practice. Because of this, epidemiological research often utilises cohort studies, whereby a large sample of individuals are followed for long periods of time. Researchers would identify risk factors by extensively recording the participants lifestyles, behaviours, or other factors at the beginning of the study, and subsequently identifying which of these individuals go on to develop a particular disease.


Heart Attacks: An example

Imagine a researcher wanted to identify lifestyle factors, that are associated with heart attacks in later life. They would select a sample from the population to study. Using a health and lifestyle questionnaire, the researcher could ask each individual about their lifestyles, such as the amount of physical activity they undertake, the amount of fast food they eat or the number of cigarettes they smoke. The researchers would then follow the participants over 10 to 15 years, and would record the number of people who suffer from a heart attack.

Using this information, and statistical analyses, we can look for associations between each risk factor and heart attacks. For example, we could split the sample into 2 groups: those who had a heart attack and those who didn't. We can then compare the frequency of different risk factors in these 2 groups, and identify which factors are more or less common in the healthier group compared to those who suffered from heart attacks. We might have found for example that individuals who smoke, are more commonly in the heart-attack group, than those in the non-heart attack group. If this is found consistently across a number of studies, it provides evidence for the association and causation between the risk factor and disease.

Applications of epidemiological research

Once a clear risk factor is identified for a disease, steps can be taken in order to prevent people from becoming exposed it. When researchers identify the link between asbestos and lung cancer or asbestosis, for example, steps were taken to stop this material from being used in building works. Techniques were also developed to dispose of existing asbestos without exposing it to individuals. Worldwide, public health systems carry out a multitude of prevention and treatment strategies in order to reduce people's risk of exposure to harmful factors. They also seek to target individuals who have are exposed to health risks, with the necessary drugs or treatments to prevent further spread of disease. This is carried out in a number of ways.


Health interventions

Health interventions are often one off actions that are undertaken in very specific groups of the population. They may seek to improve awareness of the disease risks, to immunise against infectious disease, or to remove a risk factor from a population. Sexual health interventions, for example, were used during the HIV/AIDS epidemic during the 1990's.  Interventions sought to educate people about the risks of unprotected sex, as well as  encourage people to use condoms. In doing this, the spread of disease was reduced, and people were more prepared and able to protect themselves.


Health policies

Public policy is another way that individuals are protected from health risks. They are often implemented at a national, international or even worldwide level. They often relate to risks or diseases which are likely to affect large numbers of people. Immunisation programmes for example are used to protect people from serious infectious diseases, usually from a very young age. In the UK for example, an extensive array of immunisations are offered automatically to all newborns infants and children. These prevent children from becoming infected with infectious diseases such as measles, meningitis, and polio. It also reduces the chance of such diseases spreading and becoming epidemic, in the instance of somebody being infected.



Epidemiology studies the patterns and determinants of disease within populations. In doing this, it enlightens and informs public policies and interventions which can be undertaken in the interests of public health.