Epidemiology

• •Epidemiology looks for patterns of disease or illness in groups of people to try to identify or promote further knowledge of the causes of specific diseases.

  •Information can be collected about the effects of diet, race, culture, employment, age, gender, occupation and specific local environmental conditions which can be correlated with incidence, distribution, time and place of the disease under investigation.
• •Incidence is the number of new cases within a specific time period

  •This means it is a measure of the rate at which new cases occur.

  •In the case of communicable/infectious disease you could think of it as being the risk of getting a particular disease
• •Prevalence is the proportion of a population affected by a medical condition at a specific time. it is usually expressed as a percentage, fraction or number of cases per size of population.

  •For example at the end of December 2020 there were 81,520 recorded cases of COVID-19 in the UK, meaning a prevalence of 120 cases per 100,000 population.

  •However this is not an accurate figure for prevalence as it includes only those who had a positive test for COVID-19. the true figure for prevalence includes everyone with a disease, not just those who have been diagnosed.
• •Mortality is the death rate in a population. Every death along with the cause must be reported to the authorities and registered. This data is essential in the study of disease.

  •The number of deaths each year per 1000 of the population is the mortality or death rate standardised by age and/or gender
• •Morbidity is the state of having a disease, illness, or medical condition.

  •Some examples of common morbidities are heart disease, diabetes, and obesity

  •Morbidity is often used in describing chronic (long lasting) or age related illnesses. The greater the person’s morbidity, the shorter their expected lifespan compared with healthy individuals.However, morbidity does not necessarily mean that the disease or illness is immediately life-threatening. The morbidity rate depends on the incidence and prevalence of a disease
• •A double blind trial or randomized clinical controlled trial is where volunteers are randomly assigned to 2 groups.

  •One group is given one treatment and the other group is given placebo.

  •The participants do not know which treatment they are having and neither do the people running the trial

  •One group in the trial may take a placebo drug.

  •At the end of the trial the results are compared.

  •It is important to attempt to keep everything the same except for one thing known as the variable(not consistent) and to be able to repeat and the results are the same.
• •A placebo (also known as a dummy drug) is chemically inactive but has the same appearance and method of treatment as drugs used in the trial.

  •Using a placebo allows comparison and ensures validity of results.

  •Placebo also  eliminates psychological bias.

  •In a double blind trial the doctors and nurses will not know if the individual taking part is taking the real drug or the placebo.
• •Epidemiology is not just an academic exercise; its purpose is to help understand the cause and spread of the disease so that strategies can be developed to prevent disease

  •In simple terms, epidemiology uses a systematic approach to;

  1.Count the number of cases of the disease

  2.Calculate the rate of the disease

  3.Compare rates, either over time or between different groups
• •Trends – is the disease increasing or decreasing?

  •Patterns – does it affect mostly the elderly, is it related to factors such as poverty or living conditions?

  •Study the progression of a disease

  -Looking at trends and patterns in a disease gives an insight into how the disease spreads and what type of action might be needed. Epidemiology helps track the mortality rate of a disease.

  -This gives an indication of how many times the progression of the disease is fatal and also the effect of any therapeutics.
• •Once we have an understanding of the cause of a disease, how it spreads and how quickly it spreads, we can start plan ways of treating it (therapeutic measures such as drug treatment) or ways to prevent it (such as vaccinations)

  •Epidemiological methods also allow us to monitor the effectiveness of those measures so that we can evaluate and , if necessary, change or improve them
• •Public health policy covers a wide range of issues, not just medical interventions such like drug treatments or vaccinations. Other factors that must be included in public health policy have also played an important part;

  •Improved nutrition

  •Improved sanitation (availability of clean, fresh water and removal of sewage)

  •Improved housing – (particularly a reduction in overcrowding)

  •Improved access to basic healthcare (rather than just advances in medical technology)Greater education and health promotion
• .Classification of different types of diseases or health conditions are important.

  .The World Heath Organisation (WHO) is an agency of the United Nations that promotes health and monitors disease in an attempt to achieve good health for all.

  .WHO has established a Family of International Classifications (FIC) to provide a common language for health information worldwide.
• -The most widely used classifications of disease are:

  (1) topographic, by bodily region or system,

  (2) anatomic, by organ or tissue,

  (3) physiological, by function or effect,

  (4) pathological, by the nature of the disease process,

  (5) epidemiological.
• .Good classification systems have multiple benefits:

  -They provide a common language for reporting and monitoring health and disease

  -They allow the sharing and comparing of data, making like for like comparison possible

  -They support the development of possible treatments
• .Pathological classification is made according to the nature of the disease. For example, cancer is associated with uncontrolled cell growth, while some inflammatory diseases are related to autoimmunity

  .Epidemiological classification refers to the rate of occurrence and distribution of disease in a population