Concept of Epidemiology – This book covers the entire syllabus of “Community Health Nursing” prescribed by the Universities of Bangladesh- for Basic and diploma nursing students. We tried to accommodate latest information and topics.
This book is examination friendly setup according to the teachers’ lectures and examination’s questions. At the end of the book previous university questions are given. We hope in touch with the book students’ knowledge will be upgraded and flourished. The unique way of presentation may make your reading of the book a pleasurable experience.
Concept of Epidemiology
Epidemiology:
The term of epidemiology is derived from three Greek words-
Epi- upon, on, befall
Demo- population, people, man
Logy-study of
Literally epidemiology: that which befalls man.
Epidemiology has been defined by John M. Last in 1988 as-.
“The study of distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.”
Or,
According to Weles, “Epidemiology is the study to the natural history of the disease.”
Or,
According to World Health Organization (WHO),
“Epidemiology is the study of the distribution and determinants of health-related states or events (including disease), and the application of this study to the control of diseases and other health problems. Various methods can be used to carry out epidemiological investigations: surveillance and descriptive studies can be used to study distribution; analytical studies are used to study determinants”.
[Ref: K Park/26/759]
Basic components of epidemiology:
There are three components of epidemiology-
1. Disease frequency
2. Distribution of disease
3. Determinants of disease.
1. Disease frequency: Measurement of frequency of disease, disability or death which are summarized in the form of rates and ratio.
Example: prevalence rate, incidence rate, death rate etc.
These are essential for comparing the health status with others.
2. Distribution of disease: Disease distribution is studied according to-
a. Place: Different disease predominates in different places. e.g.
➤ Ca stomach-Japan
➤ Heart disease- Developed countries
➤ Goiter-North bangle
➤ Malaria-Hill tracts
b. Time: Different disease predominates in different times. e.g.
➤ Diarrhea- Rainy season
➤ Respiratory infection- Winter
➤ Measles- Winter, early spring
➤ Food poisoning-Summer
➤ Motor car accident-weekend
c. Person: Different disease predominates in different persons. e.g.
➤ Age:
- Measles-childhood
- Cancer-middle age
- Atherosclerosis-old age
➤ Sex:
- Lung cancer, prostate cancer-male
- Breast cancer-female
➤ Occupation:
- Silicosis-coal miners
- Heart disease-sedentary workers.
➤ Social factors:
- Upper social class-coronary heart disease, HTN, DM
- Lower social class- diarrhea, TB, tetanus.
➤ Behaviors:
- Smoking- coronary heart disease, Ca lung.
3. Determinants of disease: That is, identification of causes or risk factors of disease.
Example: Social/environmental/political determinants, behavioral/individual determinants.
[Ref: K Park/26/759-611]
The aims of epidemiology:
According to International Epidemiological Association (IEA), Epidemiology has three main aims –
➤ To describe the distribution and magnitude of health and disease problems in the population.
➤ To identify the etiological factors (risk factors) in the pathogenesis of disease.
➤ To provide the data essential to planning, implementation and evaluation services for prevention, control and treatment of disease and to setting up of priorities for these services.
The ultimate aims of epidemiology:
➤To eliminate or reduce the health problem or its consequences; and
➤ To promote the health and wellbeing of society as a whole.
[Ref: K Park/26/759-61]
The purpose of epidemiology:
➤To better understand the burden and cause of health problems in human populations, and
➤ To make changes that decrease risk and improve health.
The objectives of epidemiology:
♦ General objectives:
➤ Explaining the casual mechanisms of disease and process of deviation in health.
➤ Explaining the reason for local disease occurrence.
➤ Effective planning and administration of health care service.
♦ Specific objectives:
➤ Understanding causation of disease with specific purpose.
➤ Testing validity of rational of control/intervention program.
➤ Classify disease/disability based on-
- Distribution
- Casual factors; and
- Natural history of disease
- Explaining local disease patterns.
[Ref: K Park/26/759-61]
Different measurements of epidemiology:
The measurement of epidemiology:
a. Measurement of mortality
b. Measurement of morbidity
c. Measurement of disability
d. Measurement of the presence, absence or distribution of the characteristics or attributes of the disease.
e. Measurement of natality.
f. Measurement of medical needs health care facilities, utilization of health service and other health-related events
g. Measurement of the presence, absence or distribution of the environmental and other factors suspected of causing the disease
h. Measurement of demographic variables.
[Ref: K Park/26/759-61]
Basic tools of epidemiological measurement
The basic tools of measurement in epidemiology:
1. Rates
2. Ratio
3. Proportion
1. Rate: Occurrence of some particular events (e.g. disease) in a given population during a given period of time.
Numerator (X)
Rate:……X Multiple (K)
Denominator (Y)
K- is a convenient number or bases to express the relation of X and Y
It is usual to use 100, 10,000, 100,000 or 100,0000.
Types:
1. Crude rate: Actual observation/data without change, e.g. crude birth rate.
ii. Specific rate: Actual observation/data of
a. Specific cause(e.g. TB)
b. Specific group (E.G. 5-10 years boy) c. Specific time(e.g. July, 2000)
iii. Standardized rate: Directly or indirectly adjusted or standardized e.g. Age & sex standardize rate.
2. Ratio: A ratio shows the relative sizes of two or more values.
Numerator (X)
Ratio:……………………………………………….
Denominator
RBC: WBC ratio
Sex ratio
Child-women ratio
Doctor-population ratio
3. Proportion:
The correct or appropriate relationship between the size, shape, and position of the different parts of something.
It is a ratio where numerator is a part of whole things (Denomeretor)
The number of children with scabies
Proportion:………………………………………………………………………………………………………….. X 100
The total number of children
In a class room 15 boys and 5 girls
Total 15+5=20
5
Proportion of girls:………………………………………….X 100 = 25%
20
[Ref: K Park/26/759-61]
Differences between epidemiology and clinical medicine:
| Traits | Epidemiology | Clinical medicine |
| Unit of study | Population at risk or defined population | Case or cases |
| i. Concern with | a. Disease pattern in entire population b. Both sick and health | Only sick, not healthy |
| ii. Doctor-patient relation | The investigator goes out into the community | The patient comes to the doctor |
| iii. Identify | a. Source of infection b. Mode of spread c. Future trend d. Specific control measures | Seek a diagnosis and prescribe specific treatment |
| iv. Evaluation | Prevention and therapeutic measure | No such responsibility |
| v. Idea | “Conceptual”-symbolized on the form of table and graph | Perceived by- a. clinical diagnosis b. lab diagnosis c.post mortem |
| vi. Services | Epidemiologist give comprehensive healthcare a. Preventive b. Promotive c. Curative d. Rehabilitative | Physician gives only curative health care |
[Ref: K Park/26/759-611]
Role of Field Epidemiologists/ nurses in the field of epidemiology in Providing Evidence:
Developed countries have constructed their public health and disease control strategies by using the principles of field epidemiology. Developing countries need to build and sustain human capacity in field epidemiology. Strengthened field epidemiologic capacity can serve a country in the following specific areas:
➤ Providing a response to acute problems
➤ Providing the scientific basis for program and policy decisions
➤ Implementing disease surveillance systems
➤ Supporting national health planning
➤ Making resource allocation decisions
➤ Allocating the human capacity base for national health priorities.
Specific competencies that should be developed include, but are not limited to, the ability to accomplish the following:
➤ Design, implement, and evaluate surveillance for a health event
➤ Identify and assess an actual public health problem
➤ Design and conduct a scientific investigation
➤ Analyze and interpret data from an investigation
➤ Recommend logical and practical public health actions after the analysis and interpretation of data
➤ Be proficient in all aspects of diseases of public health importance (for example, HIV and AIDS, sexually transmitted diseases, malaria, tuberculosis, and zoonoses).
[Ref: K Park/26/759-61]
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