Diese Präsentation wurde erfolgreich gemeldet.
Die SlideShare-Präsentation wird heruntergeladen. ×

Principles and methods of epidemiology.pptx

Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Nächste SlideShare
Disease control.pptx
Disease control.pptx
Wird geladen in …3
×

Hier ansehen

1 von 39 Anzeige
Anzeige

Weitere Verwandte Inhalte

Aktuellste (20)

Anzeige

Principles and methods of epidemiology.pptx

  1. 1. PRINCIPLES OF EPIDEMIOLOGY AND METHODS OF EPIDEMIOLOGICAL STUDIES Submitted To: Submitted By: Dr. Seep Mahajan Abhishek kashyap
  2. 2. CONTENT Introduction Definition Components of epidemiology Aims of epidemiology Principles of epidemiology Methods of epidemiological studies
  3. 3. INTRODUCTION Epidemiology is derived from the Greek words, Epi: means upon. Demos: mean study of population or People. Logos: means the scientific study So, epidemiology is study of disease pattern in human population or study of effects of multiple factors on human health.
  4. 4. DEFINITION The study of distribution and determinants of health related states in specified populations, and the application of this study to control health problems. Also, epidemiology  Is the basic science of public health.  Provides insight regarding the nature, causes and extent of health disease.  Provides information needed to plan and target resources appropriately.
  5. 5. COMPONENTS OF EPIDEMIOLOGY Distribution of disease Disease frequency. Determinents of disease
  6. 6. AIMS OF EPIDEMIOLOGY 1. To identify the etiological factor in disease pathogenesis. 2. To demonstrate the data required for the planning, implementation, and evaluation of services for disease prevention, control, and treatment, as well as the establishment of priorities among those services . 3. It describes the extent and distribution of health disease problems in the human population
  7. 7. PRINCIPLES OF EPIDEMIOLOGY 1) To study historically the rise and fall of disease in the population. 2) Community diagnosis. 3) Planning and evaluation. 4) Evaluation of individuals risks and chances. 5) Completing the natural history of disease. 6) Searching for causes and risk factors.
  8. 8. 1.)TO STUDY HISTORICALLY THE RISE AND FALL OF DISEASE IN THE POPULATION  It is well understood that the pattern of health and disease in a community is never consistent.  There are fluctuations over both short and long time periods.  Epidemiology is the study of disease profiles and time trends in the human population.  We can make useful projections into the future and identify emerging health problems and their correlates by studying these trends.
  9. 9. 2.)COMMUNITY DIAGNOSIS  Community diagnosis is one of the applications of epidemiology.  The identification and quantification of health problems in a community in terms of mortality and morbidity rates and ratios is referred to as community diagnosis.  It aids in the identification of at-risk individuals or groups, as well as those in need of health care.
  10. 10. 3.)PLANNING AND EVALUATION  It is about the distribution of health problems over time and space, which provides the fundamental foundation for planning and developing needed health services, as well as assessing the impact of these services on people's problems.  Evaluation is an important aspect of epidemiology.  Any measures taken to control or prevent a disease must be followed by an evaluation to determine whether the measures are effective in reducing disease frequency.
  11. 11. 4.) EVALUATION OF INDIVIDUALS RISKS AND CHANCES  One of the important tasks of epidemiologists is to make a statement about the degree of risk in a population.
  12. 12. 5.)COMPLETING THE NATURAL HISTORY OF DISEASE  Epidemiology is concerned with the entire spectrum of disease in the population.  By studying disease patterns in the community in relation to agent, host and environmental factors is in better position to fill up the gaps in the natural history of disease than a clinician.
  13. 13. 6.)SEARCHING FOR CAUSES AND RISK FACTORS  Epidemiology helps to identify the causes and risk factors of diseases.
  14. 14. METHODS OF EPIDEMIOLOGY
  15. 15. Epidemiological studies Descriptive Amount and distribution in populations person,place and time Analytic Test hypothesis, identify and quantify risk or exposure Experimental Study Types ➔ Clinical trials ➔ Preventive trials ➔ Community intervention trials Observational Study Types ➔ Case control ➔ Cohort ➔ Cross sectional Descriptive Study Types ➔ Case reports ➔ Case series ➔ Ecological studies ➔ Cross sectional
  16. 16. DESCRIPTIVE EPIDEMIOLOGY
  17. 17. DESCRIPTIVE EPIDEMIOLOGICAL STUDIES:-  To know the situation i.e, what is the problem? , what are its manifestation? OR  To describe the general characteristics of disease in relation to time, place ,person. Person: who is getting sick? Place: where is the sickness occurring? Time: when is the sickness occurring?
  18. 18. 1.) CASE REPORT  It consists of a careful and detailed report by one or more clinicians of unusual medical condition.  It represents first clue in the identification of a new disease.  It leads to formulation of new hypothesis.  EXAMPLE: Intestinal obstruction was reported in a young child.Documents showed that this child received ROTA virus vaccine 3 months ago. A detailed report about this unusual event & exposure was published in journal. The investigator formulated a hypothesis that rota virus vaccine may have been responsible for the rare occurrence of this event.
  19. 19. 2.)CASE SERIES It is the only study which depend on Routine Surveillance. EXAMPLE:- 8 cases of lung cancer were admitted to different hospitals during same period of time. Taking history from these patients showed that they were miners.This unusual circumstance suggested that the miners may been exposed to something. Investigating this circumstance showed high concentration of radon gas. A hypothesis was formulated that lung cancer is related to exposure to randon.
  20. 20. ADVANTAGES DISADVANTAGES 1.) They formulate a new hypothesis for disease occurrence. 1.) For case report, the presence of any exposure may be coincidental because it is based on a single experience. 2.) They act as trigger as they stimulate the start of analytic studies to be conducted to identify the risk factors of the disease. 2.)Lack of the comparison group in case series can either obscure the relationship or suggest an association which is not actually exist. 3.) Modification of the case series to be a case control study can be obtained by using a comparison group. 3.)Both of them cannot be used to show the causal association,i.e. Can not be used to test the hypothesis.
  21. 21. 3.)ECOLOGICAL STUDY  The source of data is the entire population.  It compares disease frequencies:- Between different population during the same period of time or In the same population at different time.  It compares 2 quantitative variables. EXAMPLE :- Correlation between one of climatic indicator (Temp.) and frequency of cerebrovascular storks.
  22. 22. FIG. SHOWS THE CORRELATION BETWEEN THE AVERAGE REGIONAL TEMP. AND FREQUENCY OF CVSS IN DIFFERENT COUNTRIES. COUNTRIES WITH HIGHEST AVERAGE TEMP. HAVE HIGHEST RATES OF CVSS AND VICE VERSA.
  23. 23. Advantages & Disadvantages of Ecological Studies ADVANTAGES DISADVANTAGES 1. Formulates new hypothesis 1.)They cannot be used for testing hypothesis 2.) Quick and Cheap 2.) Lack of ability to control
  24. 24. 4.)CROSS SECTIONAL STUDY Population Sample With exposure &with disease With exposure & without disease Without exposure & without disease Without exposure & with disease
  25. 25. EXAMPLE:- DURING THE YEAR 2019, A REPRESENTATIVE SAMPLE OF SECONDARY SCHOOL CHILDREN IN A CITY X (N=400) WERE ASKED ABOUT CONSUMPTION OF HIGH CALORIC DIET AND EXAMINED TO DETECT OBESITY. Secondary school children Sample n=400 Consumption of high caloric diet with obesity n=20 Consumption of high caloric diet without obesity n=60 No consumption of high caloric diet with obesity n=16 No consumption of high caloric diet without obesity n=304
  26. 26. ADVANTAGES & DISADVANTAGES OF CROSS- SECTIONAL STUDY ADVANTAGES DISADVANTAGES 1.)Formulation of hypothesis 1.)Can’t be used to test hypothesis 2.)Suitable for chronic diseases with long latency 2.)Can’t be used in acute diseases of short duration 3.)Quick and cheap 3.)Not suitable for rare diseases
  27. 27. ANALYTIC EPIDEMIOLOGY
  28. 28. ANALYTIC EPIDEMIOLOGY  To identify causal relationships between some risk factors and occurence of disease.  Try to answer why the disease occurs.  Their types are:- 1.) case control 2.)cohort :- -Prospective & Retrospective 3.) Comparative cross-sectional
  29. 29. OBSERVATIONAL STUDY TYPE (1.) CASE CONTROL STUDY The investigator enrolls a group of people without disease (controls). Investigator then compare previous exposures between the two groups. The control group provides an estimate of baseline or expected amount of exposure in that population. EXAMPLE:- 1. Study to determine an association between lung cancer and radon exposure. 2. Study to determine association between salmonella infection and eating at a fast food restaurant.
  30. 30. (2.) COHORT STUDY  Study population is grouped by exposure status.  Groups are then followed to determine if they develop the outcome EXAMPLE:- study to determine if smokers have a higher risk of lung cancer. EXPOSURE OUTCOME Prospective Assessed at beginning of study Followed into the future for outcome Retrospective Assessed at some point in the past Outcome has already occured
  31. 31. (A.) PROSPECTIVE COHORT STUDY:- IT IS A LONGITUDINAL COHORT STUDY THAT FOLLOWS OVER TIME A GROUP SIMILAR INDIVIDUALS(COHORTS) WHO DIFFER WITH RESPECT TO CERTAIN FACTORS UNDER STUDY, TO DETERMINE HOW THESE FACTORS AFFECT RATES OF CERTAIN OUTCOMES.
  32. 32. (B.) RETROSPECTIVE COHORT STUDY:- THESE ARE TYPE OF OBSERVATIONAL RESEARCH IN WHICH THE INVESTIGATOR LOOKS BACK IN TIME AT ARCHIVED TO EXAMINE WHETHER THE RISK OF DISEASE WAS DIFFERENT BETWEEN EXPOSED AND NON-EXPOSED PATIENTS.
  33. 33. (3.)CROSS-SECTIONAL STUDY A cross-sectional study is defined as a type of observational research that analysis data of variables collected at one given point in time across a sample population or a pre-defined subset. This study is also known as Cross- Sectional Analysis.
  34. 34. EXPERIMENTAL STUDY TYPE  Active trial to change disease determinant by the investigator who allocates the exposure & follow the subjects.  Can be viewed as a type of prospective cohort study. ETHICAL POINTS must be considered: 1. It should have beneficial effect to patients, not to harm anyone by intervention. 2. Participants should know what the experiment is and have right to refuse. 3. If any unplanned complications occur to any participant he should be excluded from the trial and treated.
  35. 35. (1.) CLINICAL TRIALS:-  It is usually used to assess efficacy of a new line drug or to compare 2 types of drugs.  Diseased subjects are randomly allocated into 2 groups, who are given “new drug” and “control group” (who are given usual drug or no drug in placebo).  Results are assessed by comparing health improvement of the 2 groups at end of trial.  Example: surgical or medical treatment of peptic ulcer
  36. 36. (2.) COMMUNITY TRIALS:-  Involve people who are not diseased and the sample is drawn from community.  Data collection takes place in the field.  EXAMPLE:- in studies carried out to assess the efficacy of new vaccine. The participant are divided into 2 groups: one who is experimental group ( will take the new vaccine) and 2nd is the control group ( will not take vaccine).  The participant will be followed to compare the level of occurence of the disease in both groups. Therefore, these groups should be alike as much as possible in all aspects other than new drug.

×