| TYPES OF EPIDEMIOLOGY | 1. Descriptive Epidemiology
2. Analytical Epidemiology |
| - Describes the occurrence of disease (cross-sectional)
- examining the distribution of disease in a population, and observing the basic features of its distribution.
antecedent to analytical epidemiology
organize and summarize data according to TIME, PLACE, & PERSON. | Descriptive Epidemiology |
| - investigating a hypothesis about the cause of disease by studying how exposures relate to disease
➔ Observational (cohort, case control, cross-sectional, ecologic study) - researcher observes association between exposure and disease, estimates and tests it
➔ Experimental (RCT, quasi experiment) - researcher
assigns intervention (treatment), and estimates and tests its effect on health outcome.
-Used to search for causes and effects, or the WHY & the HOW. | Analytic Epidemiology |
| Analytic Epidemiology two study types | 1 Observational
2 Experimental |
| 1 (cohort, case control, cross-sectional, ecologic study) - researcher observes association between exposure and disease, estimates and tests it
2 (RCT, quasi experiment) - researcher assigns intervention (treatment), and estimates and tests its effect on health outcome. | 1 Observational
2 Experimental |
| 1 disease rates change over time – the seasonal
increase in influenza with the onset of cold weather.
2 describe a health event by place to gain insight into the geographical extent of the problem.
● Residence ● Birthplace ● Place of employment ● School district ● Hospital unit, etc. ● presence of agents or vectors I climate I geology I population density I economic development I nutritional practices I medical practices | 1 Time
2 Place
(DESCRIPTIVE EPIDEMIOLOGY) |
| 1 inherent characteristics of people.
● Age● Race● Sex
2 ➔ Acquired Characteristics of this:
3➔ Activities
4 ➔ Conditions under which people live | 1 Person
2 ◆ Immunity
◆ Marital status
3 ◆ Occupation
◆ Leisure activities
◆ Use of medications/tobacco/drugs
4 ◆ socioeconomic status
◆ Access to medical care
(DESCRIPTIVE EPIDEMIOLOGY) |
| ➔ form the first step in any process of investigation.
➔ These studies are concerned with observing the distribution of disease in populations | DESCRIPTIVE STUDIES |
| STEPS in conducting a DESCRIPTIVE STUDY | 1. Defining the population.
2. Defining disease under study.
3. Describing the disease.
4. Measurement of disease
- Mortality/ Morbidity
5. Compare
- Between different population, subgroups
6. Formulate hypothesis
- On basis of all data epidemiologist form hypothesis
mnemonics: 3D Measure, Compare and Formulate |
| 1 may be the whole population or a representative
sample.
- Can also be specially selected group such as age and sex groups, occupational groups, hospital patients, school children, small community, etc.
2 Describing the disease is examined by the epidemiologist by asking three questions:__ | 1 Defining the population
2 ● When is the disease occurring –time distribution?
● Where is it occurring – place distribution?
● Who is getting the disease – person distribution? |
| Types of Distribution
(Under Describing the disease) | A. Time Distribution
B. Place Distribution
C. Person Distribution |
| A. Time Distribution
B. Place Distribution | A) 1 Short-term fluctuations
2 Periodic fluctuations
3 Long-term or secular trends
B) 1 International variations
2 National Variations
3 Rural - urban differences
4 Local distributions |
| C. Person Distribution | 1 Age
Measles is common in children,
Cancer in middle age
Degenerative diseases in old age.
2 Sex
Women- Lung cancer-less
Hyperthyroidism- more
3 Social Class
Diabetes, Hypertension– upper class |
| 1 Short-term fluctuations
give the types and then examples
(A. Time Distribution) | 1 Common source epidemics.
Single exposure/point source:
ex. bhopal tragedy
2 Propagated-infectious
ex. Hepatitis A |
| 1 Periodic fluctuations
give the types and then examples
(A. Time Distribution) | 1 Seasonal
ex. measles (early spring)
2 Cyclic
ex. in pre-vaccinated era (peak 2-3 years) |
| 1 International Variations; give examples
2 National Variations; give examples | 1 ○ Cancer stomach very common
in Japan less common in US
○ Oral cancer- India
○ Breast cancer-
low-japan,
high-western.
2 Distribution of fluorosis |
| 1 Rural - urban differences; give examples
2 Local distributions; give examples | 1 ○ CVD, Mental illness more common in urban areas.
○ Skin diseases, worm infestations more common in
rural areas.
2 ○ Spot maps - John Snow in
London to incriminate water
supply as cause of cholera
transmission in London. |
