EPIDEMIOLOGY MAJOR PARAMETERS OF DESCRIPTIVE EPIDEMIOLOGY
- derived from the Greeek word “epidemios” meaning “prevalent” 2. Prevalence- is used to indicate what proportion of a given
population is affected by a condition at a given point in
- is the study of the distribution and frequency of disease and injury
time. It is expressed as a percentage of the population and it
in human population and those making groups susceptible to
ranges from 0% to 100%.
diseasae or injury.
PREVALENCE= cases/population x 100%
USES OF EPIDEMIOLOGY:
Ex. If we examined 200 school children in November 2004, and
- It is used to delineate disease patterns in the community.
found that 50 had gingivitis, we could say that prevalence of
(this is of value to dentists involved in program planning for
gingivitis in this population in nov 2004 was 25%
dental care delivery)
- It is useful in determining the needs of the population
DIVISIONS OF EPIDEMIOLOGY II. ANALYTICAL EPIDEMIOLOGY
1. Descriptive Epidemiology - Is most often used in studies to determine the etiology of a
2. Analytical Epidemiology disease.
3. Experimental Epidemiology
3 study designs to determine the etiology of a disease:
DESCRIPTIVE EPIDEMIOLOGY- is use to aid in the conceptualization
a. Prospective Cohort Study
and quantification of the disease status of the community.
b. Case Control Study
MAJOR PARAMETERS OF DESCRIPTIVE EPIDEMIOLOGY: c. Retrospect Follow-up Study
1. INCIDENCE- is the number of cases that will occur within a PROSPECTIVE COHORT STUDY
population during a specified time period.
- It is referred to as simply cohort study, is the closest to
- It is expressed as a rate, that is, cases per population per
experimental research in epidemiology.
time. The range is from zero to infinity.
- This study is conducted on a general population that is
Incidence Rate (IR)= Cases/Person/Time followed through time to see which members or outcomes
in question.
Example: 50 people in a city of 200,000 died of oral cancer during
the year of 2004 , we can expressed the rate of death cause by oral Ex.
cancer in this population as 50 deaths per 200,000 persons per year.
1. A prospective cohort study on poor oral hygiene and III. EXPERIMENTAL EPIDEMIOLOGY
pancreatic cancer risk - is used primarily in intervention studies. Once etiology of a
2. Risk factors for tooth loss adults; a population-based disease has been established, the researcher may then wish
prospective cohort study to determine the effectiveness of a program of prevention
or therapy.
CASE CONTROL STUDY
- one method of doing so is by selecting an experimental
-It is conducted using a population that has a disease and a population for which the program has been designed.
matching population does not have a disease.
- The researcher may then divide the experimental
- researcher uses questionnaires and medical histories to review population into 2 groups, a study group that will receive the
past events and exposures preventive or therapeutic treatment and a control group
- it is relatively inexpensive and requires a fairly short period of time that will not.
to obtain results.
RETROSPECTIVE FOLLOW-UP STUDY
- It is used to evaluate the effect that a specific exposure has
had on a population
- It is commonly used in area of occupational health hazards.
- The study starts with an exposure in time past and
evaluates the histories of those exposed through to time
present
- It is relatively easy and inexpensive, provided that a select
exposure group is available and that the follow-up can be
obtained.
Ex.
1. Evaluation of an Oral Health Promotion and Preventive
Programme: A Case-Control Study
2. Caries reduction related to the use of fluorides: A
Retrospective Cohort Study
