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Epidemiology II
By
Dr.Sabah M.A.Abdelkader
Assist. Prof. of Public Health
Objectives
By the end of this session, students should
be able to:
 Define health correctly.
 Explain
association
with
disease
causation.
 Identify health and disease spectrum.
 Discuss dimensions of health.
 Identify determinants of health.
 Discuss iceberg phenomenon of diseases.

Introduction
Health is one of those terms which most
people find it difficult to define.
 Therefore, many definitions of health
have been offered from time to time.
 Understanding health is the basis of
health care.
 Health is not perceived same way by all
members of a community including
professionals.

Concepts of health
Biomedical concept:
 Absence of disease. Minimized role of
different determinants of health.
 Ecological concept:
 Equilibrium between man and environment.
 Psychosocial concept:
 Both biological and social phenomena.
 Holistic concept:
 All above concepts, multifactorial influence.

Definitions of health
Being sound in body, mind or spirit.
 Soundness of body or mind which
function duly and efficiently.
 A state of relative equilibrium of body form
and function resulting from dynamic
adjustment to forces that disturb it.
 A condition or quality of human organism
expressing adequate functioning of
organism in given conditions, genetic and
environmental.

WHO definition of health
Health is a state of complete physical,
mental and social wellbeing not merely
absence of disease or infirmity.
 Recently added: ability to lead a socially
and economically productive life.
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Some definitions related to
concept of health and disease
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Disease is physiological dysfunction
Illness is a subjective state of the person who feels
aware of not being well.
Sickness is a state of social dysfunction i.e., a role
that the individual assumes when ill.
Infection (germ theory): Entry& development and
multiplication of micro-organism inside human body
Epidemiological triad: Agent, Host, Environment.
Multifactorial causation: New types of diseases,
the so called “Modern” diseases of civilization.
Cont.
Chronic diseases: all impairments or
deviations from normal, with one or more of
the following characteristics:
 Permanent, leave residual disability, are
caused by non- reversible pathological
alteration, and require a long period of
supervision, observation or care.
 NB: no international definition of long- term.
 Many consider chronic conditions are those
that having duration of at least 3 months.

Cont.
Web of causation theory:
 Considers all the predisposing factors of
any
type
and
their
complex
interrelationship with each other.
 Provides a model which shows a variety
of possible intervention to reduce the
disease.

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Association and disease causation
Association:
 Concurrence of two variables more often
than would be expected by chance.
 Correlation:
 Indicates degree of association between
two characteristics.
 Does not imply association. (temporal
relation)
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Cont.
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I- Spurious association: (not real)
UK study perinatal mortality 5.4/1000 home del.
27.8/1000 hospital deliveries.
II- Indirect association: (confounding factors)
e.g endemic goitre in high altitudes.
III- Direct (causal) association:
A- one-to one e.g tubercle bacilli → TB
Hemolytic streptococci→ scarlet fever or AFT
B- Multifactorial non-communicable diseases
through synergistic or commulative effects.
Health and disease Spectrum
There is no single cut-off point.
 The lowest point on the health-disease
spectrum is death and the highest point
corresponds to the WHO definition of
positive health.
 There are degrees or "levels of health",
as there are degrees or severity of
illness.

Cont.
The spectral concept
of
health
emphasizes that the health is not static; it
is a dynamic phenomenon and a process
of continuous change.
 What is considered maximum health
today may be minimum tomorrow.
 It implies that health is a state, not to be
attained once and for all, but ever to be
promoted, preserved, and restored when
impaired.

Health – disease spectrum
+ ve
Positive health
Better health
Freedom from disease
Unrecognized disease
Mild disease
Severe disease
- Ve
Death
Dimensions of health
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Main dimensions: (WHO definition)
1- Physical: perfect functioning of body (wide).
At community level evaluated by: DR,IMR, life
expectancy.
2- Mental: ability to respond with flexibility to
varied experiences in life.
A state of balance and harmony with others.
Relates to cognition.
Mental health is one key to good health.
3- Social: social skills, social functioning, ability
to see oneself as a member of society.
Harmoney , integration within an individual.
Other dimensions:
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4- Spiritual: integrity, principles, ethics,
purpose in life, commitment to our creator.
5- Emotional: relates to feeling, psychology.
Differs or related to mental dimension???
6- Vocational: new, when work is fully
adapted to human goals and capacities, work
plays a role in promoting physical and mental
health. Self realization in work is a source of
satisfaction. (sudden loss of job???)
7others:
philosophical,
cultural,
environmental,
educational,
nutritional,
preventive and curative.
Determinants of health
Biological:
 Genetics: Physical, mental traits.
 Sociocultural:
 Health requires promotion of healthy life
style.
 Environmental:
 Internal: tissues, organs, systems.
 External: everything to which humans are
exposed to after conception.

Cont.
 Socioeconomic:
 Economic, education, occupation, marital
status, political.
 Health services:
 Good care is expected from effective
health service.
 Aging of population:
 ↑chronic diseases and disabilities.
 Gender:
 Consequences of violence, reproductive
health services.
Other factors:
Transition from post industrial age to
information technology.
 Communication revolution.
 Mass media.
 Social welfare.

Medicine is not the sole contributor
To health and wellbeing of population
( Intersectoral contributions)
Iceberg phenomenon
(Natural history of disease)
Cont.
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The vast submerged portion of the iceberg
represents the hidden mass of disease (latent,
inapparent, presymptomatic, and undiagnosed
cases, and carriers in the community.
 Hypertension, diabetes, anemia, malnutrition,
mental illness are examples.
 The hidden part of the iceberg thus
constitutes
an
important,
undiagnosed
reservoir of infection or disease in the
community, and its detection and control is a
challenge to modern techniques in preventive
medicine.

Thank you