Epidemiology II By Dr.Sabah M.A.Abdelkader Assist. Prof. of Public Health

Epidemiology II
Dr.Sabah M.A.Abdelkader
Assist. Prof. of Public Health
By the end of this session, students should
be able to:
 Define health correctly.
 Explain
 Identify health and disease spectrum.
 Discuss dimensions of health.
 Identify determinants of health.
 Discuss iceberg phenomenon of diseases.
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
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
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.
Some definitions related to
concept of health and disease
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.
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.
Web of causation theory:
 Considers all the predisposing factors of
interrelationship with each other.
 Provides a model which shows a variety
of possible intervention to reduce the
Association and disease causation
 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
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
The spectral concept
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
Health – disease spectrum
+ ve
Positive health
Better health
Freedom from disease
Unrecognized disease
Mild disease
Severe disease
- Ve
Dimensions of health
Main dimensions: (WHO definition)
1- Physical: perfect functioning of body (wide).
At community level evaluated by: DR,IMR, life
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:
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???)
preventive and curative.
Determinants of health
 Genetics: Physical, mental traits.
 Sociocultural:
 Health requires promotion of healthy life
 Environmental:
 Internal: tissues, organs, systems.
 External: everything to which humans are
exposed to after conception.
 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)
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
reservoir of infection or disease in the
community, and its detection and control is a
challenge to modern techniques in preventive
Thank you