5.principles and methods of epidemiology

Public Health

1. Principles and Methods of Epidemiology RDM 205 Rural Health and Well-being Rajeev Kumar

2. “ I kept six honest serving men; they taught me all I know. Their names are what, why, when, how, where, and who.”

3. What is Epidemiology? As defined by John M. Last (1988) “ Epidemiology is the study of the distribution and determinants of health related states or events in specified populations, and the applications of this study to control of health related problems”

4. Three pillars of Epidemiology Disease frequency Distribution of disease Determinants of disease

5. Disease frequency Epidemiology is the measurement of frequency of disease, disability or death and summarizing this information in form of rates and ratio. (details will be discussed later)

6. Distribution of disease Disease or health related matter are not uniformly distributed in human population. Those are distributed in patterns in community, and epidemiology address those variations or patterns. This aspect is known as descriptive epidemiology

7. Determinates of disease It identify the underlying causes ( or risk factors). This is the real substance of epidemiology

8. Aims of epidemiology It describes the distribution and magnitude of health and disease problems in human population To identify the aetiological factor (risk factors) in the pathogenesis of disease To prove the data essential to the planning, implementation and evaluation of services for the prevention, control, and treatment of disease and to setting up of priorities among those services

9. Epidemiology approach Asking questions 2. Making comparisons

10. (A). Asking questions ( activity based on given article) What is the event / problem? What is the magnitude ? Where did it happen? When did it happen? Who are affected? Why did it happen?

11. (B). Questions related to health action ( activity based on given article) What can be done to reduce the problem and its consequence? How it can be prevented in the future ? What action should be taken by the communities? By the health service? By other sectors? Where and for whom these activities be carried out ? What resources are required? How far the activities to be organized ?

12. Making comparisons There may be comparisons of two or more groups There may be comparisons between communities or regions or genders Before comparison, we need to consider the comparability As is control and cohort studies ( will be discussed later)

13. Basic measurements in epidemiology Measurement of mortality Measurement of morbidity Measurement of disability measurement of presence, absence or distribution of the characteristics or attributes of the diseases Measurement of medical needs, health care facilities utilization Measurement of the presence, absence or distribution of the environmental and other factors suspected of causing the disease. Measurement of demographic variables

14. Types of variables Variate: any piece of information referring to the patients or disease, it is of two types (1) discrete (2) continuous Circumstance: Any factor in the environment that might be suspected of causing a disease ( air pollution, polluted water)

15. Tools of measurement Rates Ratio Proportion

16. Rates Suppose there were 500 deaths from traffic accidents in Ranchi.. These are just number.... It conveys no meaning to epidemiologist It is not comparable with road accidents deaths with another city Then what ????

17. What is rate??/ Rate measures the occurrence of some particular event in a population during given time. It is statement of risk of developing a condition Death rate = number of death in one year/mid-year population X 1000

18. Example of death rates

19. Specific death rates

20. Ratio

21. Proportion

22. Examples of proportion

23. incidence

24. Prevalence It refers specifically to all current cases (old and new) existing at a given point of time, over a period in a given population It is of two types: 1. Point prevalence 2. period prevalence

25. Relationship between prevalence and incidence

26. Epidemiological methods observational studies Experimental studies

27. Observational studies Cross-sectional studies Case control Cohort studies Longitudinal studies Types of cohort

28. Experimental studies Randomized control trial

29. Description of experimental studies Dependent variable Independent variables Mediators /moderators variables What is randomization? What is control? What is blind? How many types of blind? Why there is blind?

30. Discussion and queries ??? Keep learning !!!