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Biology in Focus, HSC Course Glenda Childrawi, Margaret Robson and Stephanie Hollis A Search For Better Health Topic 11: Epidemiology.

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Presentation on theme: "Biology in Focus, HSC Course Glenda Childrawi, Margaret Robson and Stephanie Hollis A Search For Better Health Topic 11: Epidemiology."— Presentation transcript:

1 Biology in Focus, HSC Course Glenda Childrawi, Margaret Robson and Stephanie Hollis A Search For Better Health Topic 11: Epidemiology

2 DOT Point(s) identify and describe the main features of epidemiology using lung cancer as an example

3 Introduction The incidence of a particular disease, the cause of which is unknown, is increasing in a population. This disease is causing severe symptoms for the sufferers, and quite often results in death.

4 Introduction This leads scientists to ask the questions: Is there a pattern to the occurrence of this disease? What could be the cause of this disease? What control measures can be put in place to help prevent this disease? In order to answer these questions about the disease, an epidemiological study could be undertaken.

5 Introduction Epidemiological studies play a major role in identifying patterns in the occurrence of disease, identifying the possible cause of disease and determining the strategies that would be most effective in controlling disease in the population.

6 Epidemiology Epidemiology is the scientific study of patterns of occurrence of disease in human populations and the factors that affect these patterns. It describes, statistically analyses and hypothesises as to the cause of the disease in the population.

7 Epidemiology Epidemiology can be used to study both infectious and non- infectious diseases as well as events such as suicides, car accidents and work-related accidents.

8 Epidemiology Results from epidemiological studies are used by public health authorities to develop strategies to control disease and improve public health. Epidemiological studies can also be used to evaluate those strategies that are already in place.

9 Epidemiology There are three major types of epidemiological studies: 1. descriptive 2. analytical 3. intervention.

10 Epidemiology 1. Descriptive studies are usually the first type of study completed when investigating the cause of a disease. These provide information about the patterns of the disease, including the frequency of the disease, which section of the population is affected (age, gender, occupation, socioeconomic status and so on), the geographical location and whether there was a particular time period in which individuals were affected.

11 Epidemiology In an early epidemiological study launched to determine the cause of lung cancer, the data collected included, amongst other things, information about the age, sex, smoking habits, diet, occupation and drinking habits of both smokers and non-smokers.

12 Epidemiology 2. Analytical studies occur once a descriptive study has been completed and are used to collect more data, which is then statistically analysed to develop hypotheses as to the likely cause(s) of the disease. The morbidity (number of cases of the disease) and the mortality (percentage of the population that dies from the disease) are two indicators that can be used in these studies.

13 Epidemiology Data about the incidence (number of new cases in a specific period) and the prevalence (number of people affected at any one time) are also compiled in these studies.

14 Epidemiology Case-control studies and cohort studies are two types of analytical studies that can be used: Case-control studies compare people with the disease (case) to people without the disease (control) and look for differences in exposure to the possible causes of the disease.

15 Epidemiology A case-control study, set up in London in 1947 by Richard Doll, compared patients with lung cancer to patients with other conditions. Information about many factors in their life, including their smoking habits, was collected. The results of this study showed that most of the individuals with lung cancer were smokers and suggested a link between smoking and lung cancer.

16 Epidemiology Cohort studies involve studying two or more similar groups of people who are free of the disease. These groups differ in one main factor, that being their exposure to the potential cause of the disease.

17 Epidemiology These groups are followed over a long period of time to compare the resulting incidence of the disease that is being studied. For example, after the 1947 case- control study that established a link between smoking and lung cancer, a cohort study was set up in England in 1951 by A. B. Hill.

18 Epidemiology This study followed more than 40 000 doctors over a 10-year period. One group of doctors were smokers (the test group) and the other group were non-smokers (the control group). At the end of the study it was found that the test group had a much higher incidence of lung cancer than the control group. This study also revealed that the greater the number of cigarettes smoked daily, the greater the chance of dying from lung cancer.

19 Epidemiology 3. Intervention studies are used to test the effectiveness of a treatment (e.g. a clinical trial of a new drug), or the effectiveness of a public health campaign to change the behaviour of the population as a whole in order to decrease the incidence of the disease. For example, the effectiveness of campaigns such as the ‘Quit’ campaign to decrease the number of people smoking is evaluated using a study such as this.

20 Epidemiological Studies Epidemiological studies should: be conducted over a long period of time study very large sample sizes (thousands) collect a range of relevant data from a large group of both affected and unaffected people (case-control). This relevant data could include age, sex, diet, occupation, lifestyle and exercise habits

21 Epidemiological Studies have participants that represent a broad range of society and lifestyles use control groups who are not exposed to the potential cause of disease but are similar in all other respects to the test group (cohort studies) collect data on the incidence, prevalence, mortality and morbidity rates of the disease being studied

22 Epidemiological Studies statistically analyse the data to identify patterns and trends in the occurrence of the disease identify the possible cause of the disease and any risk factors develop a management plan with strategies to control or eliminate the disease and educate the public evaluate the effectiveness of control and treatment programs.

23 Homework -Students to complete Smoking and Lung Cancer Activity

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