2. Objectives
• Define Epidemiology
– Origin of the term “Epidemiology”
• Difference between: Epidemic, Endemic,
Pandemic
• Uses of Epidemiology
• Levels of prevention
1
3. “Epidemiology is primarily concerned with
identifying the important factors or variables that
influence a health outcome of interest.”1
Definition 1
4. “Epidemiology is the study of the occurrence and
distribution of health-related states or events in
specified populations, including the study of the
determinants influencing such states and the
application of this knowledge to control the health
problems .”2
Definition 2
6. “Epidemiology is the study of health and disease
in a population.” 3
-The population dimension is a distinctive
characteristic of epidemiology, why?
- We tend to think of medicine dealing with health and disease
in individuals rather than population,
- Health & diseases of a population is less prominent in the
minds of most people.
Definition 3
A more general definition :
7. The basic premise of
epidemiology is…
• Disease does not occur at
random, but rather in patterns
that reflect the operation of
underlying factors.
9. What is the difference?
• epi (among) + demos = epidemic
• en (in) + demos = endemic
• pan (all) + demos = pandemic
10. What is the difference?
• Epidemic: Occurrence of disease in excess of
the expected rate. Epidemiology is the “study
of epidemics”.
• Endemic: The usual, expected rate of disease
over time.
• Pandemic: A worldwide epidemic. Epidemics
that affect several countries or continents.
12. Uses of Epidemiology7
1) To study the history of disease
Useful for studying future ‘projections’ and predictions of trends
Useful for planning health services and public health
2) Community diagnosis
Studying the presence, nature, and distribution of health and
disease among population. As well as the dimensions of these in
incidence, prevalence and mortality (will come back to those terms)
3) To study and assess the available health services
Forming comparative studies between populations based on
1) The determination of needs and resources of a
population
2) Analysis of the available services
3) Finally, evaluation of the available services
13. Uses of Epidemiology7
4) To estimate the individual's chances and risks of disease.
The estimation is based on the common experience
The risk of individual’s risk affects risk of populations/groups
5) Completing the clinical picture
Identification of all types of cases in proportion and their
diagnostic processes
Cause-effect relationships are determined
E.g. smoking frequently cause higher risk for lung cancer
6) Identify syndromes
Establishing criteria to define syndromes
E.g. Down syndrome, sudden death in infants, etc.
14. Uses of Epidemiology7
7) To determine the causes of health and disease
Finding the causes can be through studying the differences of
health/disease rates between different groups
Determination of disease sources or causes allows us to control,
prevent, eliminate disease, injury, disability, or death rates.
16. Levels of prevention3
Primary
The prevention of disease from occurring.
E.g. needle exchange programs to prevent the spread
of HIV, vaccination programs, smoking prevention
programs, etc.
17. Levels of prevention3
Secondary
The prevention of progression of early-staged disease
(i.e. people who carry the agent but are not symptomatic yet)
E.g. Treating asymptomatic HIV-infected patients with
antiretroviral agents to delay the onset of AIDS. Screening tests
such as for cervical cancer via Pap smears.
18. Levels of prevention3
Tertiary
The prevention of disability from
advanced/complex/long-lasting diseases and the
rehabilitation of the individual to functional capacity.
E.g. Cardiac or stroke rehabilitation programs
How to define disease, exposure, control variable from a real research paper?
Contineous and categorical variables.
ActivEpi Companion Textbook by David Kleinbaum
Distribution: Frequency or occurrence over space and time
M. Porta, A dictionary of Eidmeiology …..
tRodolfo Saracci a very short intro..
Distribution. Epidemiology is concerned with the frequency and pattern of health events in a population. Frequency includes not only the number of such events in a population, but also the rate or risk of disease in the population. The rate (number of events divided by size of the population) is critical to epidemiologists because it allows valid comparisons across different populations.
tRodolfo Saracci a very short intro..
Epidemiology for Public Health Practice
By Robert H. Friis, Thomas A. Sellers
In historical study of the health of the community and of the rise and fall of diseases in the population; useful ‘projections' into the future may also be possible.
For community diagnosis of the presence, nature and distribution of health and disease among the population, and the dimensions of these in incidence, prevalence, and mortality; taking into account that society is changing and health problems are changing.
To study the workings of health services. This begins with the determination of needs and resources, proceeds to analysis of services in action and, finally, attempts to appraise. Such studies can be comparative between various populations.
To estimate, from the common experience, the individual's chances and risks of disease.
To help complete the clinical picture by including all types of cases in proportion; by relating clinical disease to the subclinical; by observing secular changes in the character of disease, and its picture in other countries.
In identifying syndromes from the distribution of clinical phenomena among sections of the population.
In the search for causes of health and disease, starting with the discovery of groups with high and low rates, studying these differences in relation to differences in ways of living; and, where possible, testing these notions in the actual practice among populations.
To estimate, from the common experience, the individual's chances and risks of disease.
To help complete the clinical picture by including all types of cases in proportion; by relating clinical disease to the subclinical; by observing secular changes in the character of disease, and its picture in other countries.
In identifying syndromes from the distribution of clinical phenomena among sections of the population.
In the search for causes of health and disease, starting with the discovery of groups with high and low rates, studying these differences in relation to differences in ways of living; and, where possible, testing these notions in the actual practice among populations.
Taken from Morris JN, Uses of Epidemiology.4
http://ije.oxfordjournals.org/content/30/5/1146.full