Transcript File

Faculty of Medicine
Introduction to Community Medicine Course
(31505201)
Unit 4 Epidemiology
Introduction to Epidemiology
Levels of Prevention
By
Hatim Jaber
MD MPH JBCM PhD
(6+8)-11- 2016
1
Introduction to unit 4 Epidemiology
• Definition , History of Epidemiology
Purpose/Use of Epidemiology
• Concepts in the infectious diseases
• Disease Causation
• Measurements of Morbidity and Mortality
• Levels of prevention
• Sources of Data and methods of data
collection
• Epidemic Investigation and Management
• Epidemiological Surveillance
2
Presentation outline
Time
Health promotion, Prevention and
Control principles
Levels of Prevention- concepts
Uses and characteristics of
different levels
Control of diseases
12:00 to 12:10
12:10 to 12:20
12:20 to 12:40
12:40 to 12:50
3
“Prevention is better then cure”
4
5
Disease Prevention Overview
• Prevention is a cornerstone concept in public
health
– If it cannot be prevented, try to reduce its impact
• Often tailored to a specific disease or risk
• Prevention may occur at individual or
population levels
6
Health-to-Death Continuum
• Think about various levels of healthiness, sickness, and death
– Activities to reduce disease and increase health by where they are
initiated on the continuum
7
Relationship between Continuum and Health
Promotion & Disease Prevention
• Health Promotion – optimize overall health. LEFT side
• Disease Prevention – reduce occurrence and impact of
specific diseases. RIGHT side
8
9
(I) Prevention
• The goals of medicine are to promote
health, to preserve health, to restore
health when it is impaired, and to
minimize suffering and distress.
• These goals are embodied in the word
"prevention"
10
Prevention; Definition and Concept
• Actions aimed at eradicating, eliminating or
minimizing the impact of disease and disability, or if
none of these are feasible, retarding the progress of
the disease and disability.
• The concept of prevention is best defined in the
context of levels, traditionally called primary,
secondary and tertiary prevention. A fourth level,
called primordial prevention, was later added.
11
Determinants of Prevention
• Successful prevention depends upon:
–
–
–
–
a knowledge of causation,
dynamics of transmission,
identification of risk factors and risk groups,
availability of prophylactic or early detection and
treatment measures,
– an organization for applying these measures to
appropriate persons or groups, and
– continuous evaluation of and development of procedures
applied
12
Preventable Causes of Disease
BEINGS
Biological factors and Behavioral Factors
Environmental factors
Immunologic factors
Nutritional factors
Genetic factors
Services, Social factors, and Spiritual factors
[JF Jekel, Epidemiology, Biostatistics, and Preventive Medicine, 1996]
13
Leavell’s Levels of Prevention
Stage of disease
Level of prevention
Type of response
Pre-disease
Primary Prevention
Health promotion and
Specific protection
Latent Disease
Symptomatic Disease
Secondary prevention
Tertiary prevention
Pre-symptomatic
Diagnosis and treatment
•Disability limitation for
early symptomatic disease
•Rehabilitation for late
Symptomatic disease
A fourth level, called primordial prevention, was later added.
14
Primordial prevention
• Pri-mordial prevention consists of
actions and measures that inhibit the
emergence of risk factors in the form of
environmental, economic, social, and
behavioral conditions and cultural patterns of
living etc.
15
Primordial prevention (cont.)
• It is the prevention of the emergence or development
of risk factors in countries or population groups in
which they have
not yet appeared
• For example, many adult health problems (e.g.,
obesity, hypertension) have their early origins in
childhood, because this is the time when lifestyles are
formed (for example, smoking, eating patterns,
physical exercise).
16
Primordial prevention (cont.)
• In primordial prevention, efforts are directed
towards discouraging children from adopting
harmful lifestyles
• The main intervention in primordial prevention is
through individual and mass education
• Primordial prevention, a new concept, is
receiving special attention in the prevention of
chronic diseases
17
Primary prevention
• Primary prevention can be defined as the action
taken prior to the onset of disease, which removes
the possibility that the disease will ever occur.
• It signifies intervention in the pre-pathogenesis
phase of a disease or health problem.
• Primary prevention may be accomplished by
measures of “Health promotion” and “specific
protection”
18
Primary prevention (cont.)
• It includes the concept of "positive health", a
concept that encourages achievement and
maintenance of "an acceptable level of health that
will enable every individual to lead a socially and
economically productive life".
• Primary prevention may be accomplished by measures
designed to promote general health and well-being,
and quality of life of people or by specific protective
measures.
19
Primary Prevention
• Goal:
• Reduce number of new cases
• Rationale:
• By reducing exposure rates and increasing resistance,
can reduce number of new cases
• Target population:
• Those who are most likely to be exposed and/or could
increase their resistance
• Typical activities:
• Remove or reduce source of the risk
• Educate and make aware of disease risk
– Include behavioral changes to reduce exposure
• Improve general health
• Outcome measure: incidence of exposure; incidence of
disease
20
Primary prevention
Achieved by
Health promotion
• Health education
• Environmental
modifications
• Nutritional interventions
• Life style and behavioral
changes
Specific protection
•
•
•
•
•
Immunization and
seroprophylaxis
Use of specific nutrients or
supplementations
Protection against
occupational hazards
Safety of drugs and foods
Control of environmental
hazards, e.g. air pollution
21
Health promotion …….
“is the process of enabling people to
increase control over and to improve their
health” (Ottawa Charter ’86)
“involves the facilitation of skills in individuals
and change in environments which impact
positively on health” (Vic Health 2005)
“is everyone’s business” (CEO DHCS 2004)
22
Health promotion
not directed against any
• It is
particular
disease, but is intended to strengthen the
host through a variety of approaches
(interventions).
The well-known interventions in this area are:
• health education
• environmental modifications
• nutritional interventions
• lifestyle and behavioral changes
23
24
25
Approaches for Primary
Prevention
• The WHO has recommended the following
approaches for the primary prevention of
chronic diseases where the risk factors are
established:
– a. Population (mass) strategy
– b. High -risk strategy
26
Population (mass) strategy
• “Population strategy" is directed at the whole population
irrespective of individual risk levels.
• For example, studies have shown that even a small reduction
in the average blood pressure or serum cholesterol of a
population would produce a large reduction in the incidence
of cardiovascular disease
• The population approach is directed towards socioeconomic, behavioral and lifestyle changes
27
High -risk strategy
• The high -risk strategy aims to bring
preventive care to individuals at special risk.
• This requires detection of individuals at high
risk by the optimum use of clinical methods.
28
Example Infectious Disease
• Disease: Seasonal influenza
• Primary prevention:
–
–
–
–
target population – everyone; all ages
Goal – reduce number of cases of flu
Rationale – reduce exposures; bolster immune system
Actions
• Education: cough and sneeze etiquette, hand washing, know risk groups
• Immunization: vaccination to develop antibodies
• Interventions at the individual level:
– vaccinate; good nutrition, sleep, and exercise to optimize health; good
cough/sneeze etiquette; frequent hand washing; avoid others who are
sick
• Interventions at the community/population level:
– Provide access to vaccines
– Use Public Service Announcements (PSAs) to educate public
– Prepare plans for schools, worksites, and hospitals/clinics for outbreak
29
Secondary prevention
• It is defined as “ action which halts the progress of a
disease at its incipient stage and prevents complications.”
• The specific interventions are: early diagnosis (e.g. screening
tests, and case finding programs….) and adequate
treatment.
• Secondary prevention attempts to arrest the disease
process, restore health by seeking out unrecognized disease
and treating it before irreversible pathological changes take
place, and reverse communicability of infectious diseases.
• It thus protects others in the community from acquiring the
infection and thus provide at once secondary
prevention for the infected ones and primary
prevention for their potential contacts.
30
Early diagnosis and treatment
• WHO Expert Committee in 1973 defined early
detection of health disorders as “ the detection of
disturbances of homoeostatic and compensatory
mechanism while biochemical, morphological and
functional changes are still reversible.”
• The earlier the disease is diagnosed, and treated
the better it is for prognosis of the case and in the
prevention of the occurrence of other secondary
cases.
31
• Goal:
Secondary Prevention
• Reduce number of new cases; reduce number of severe
cases
• Rationale:
• By reducing number of exposures and early disease that
progress to more severe disease, mortality and morbidity
can be reduced
• Target population:
• Those who have been exposed to the disease-causing agent
or have early symptoms of the disease
• Typical activities:
• Screening for exposure and/or disease
• Post-exposure prophylaxis
• Early treatment to reduce impact of disease/reverse course
• Outcome measure: incidence of disease
32
Example Infectious Disease
• Disease: Seasonal influenza
• Secondary prevention:
–
–
–
–
target population – everyone who has been exposed to the virus
Goal – reduce number and severity of cases of flu
Rationale – early treatment to reduce severity of disease
Actions
• Screening: identify those who are most likely exposed from those who are not
• Early treatment
• Immunization: vaccination to develop antibodies
• Interventions at the individual level:
– Post flu symptoms and suggestions for self-care
– Provide antiviral within 48 hours of symptom onset
• Interventions at the community/population level:
– Use quarantine or isolation measures; ban gatherings of large groups; travel
restrictions
– Send sick children home from school; enforce sick leave at work
33
Tertiary prevention
• It is used when the disease process has advanced
beyond its early stages.
• It is defined as “all the measures available to reduce
or limit impairments and disabilities, and to
promote the patients’ adjustment to irremediable
conditions.”
• Intervention that should be accomplished in the
stage of tertiary prevention are disability limitation,
and rehabilitation.
34
Tertiary Prevention
• Goal:
• Reduce number of complications, deaths
• Rationale:
• By reducing disease severity and increasing recovery, can
reduce number of premature deaths or complications
• Target population:
• Those who have disease and need treatment
• Typical activities:
• Treatment tailored to the patient
• Rehabilitation to promote recovery
• Outcome measure: incidence of death and longterm disability
35
Disability limitation
disease
impairment
disability
handicap
36
Impairment
• Impairment is “any loss or abnormality
of psychological, physiological or anatomical
structure or function.”
37
Disability
• Disability is “any restriction or lack of
ability to perform an activity in the manner
or within the range considered normal for
the human being.”
38
Handicap
• Handicap is termed as “a disadvantage
for a given individual, resulting
from an impairment or disability, that limits
or prevents the fulfillment of a role in the
community that is normal (depending on age,
sex, and social and cultural factors) for that
individual.”
39
Rehabilitation
• Rehabilitation is “ the combined and
coordinated use of medical, social,
educational, and vocational measures for
training and retraining the individual to the
highest possible level of functional ability.”
Rehabilitation
Medical
rehabilitation
Vocational
rehabilitation
Social
rehabilitation
Psychological
rehabilitation
40
Example Infectious Disease
• Disease: Seasonal influenza
• Tertiary prevention:
– target population – everyone who has influenza
– Goal – reduce number and severity of flu-related complications and deaths
– Rationale treatment and rehabilitation can reduce deaths and help return
individual to a normal lifestyle
– Actions
• Provide supportive care and early treatment of complications
• Use rehabilitation to increase recovery of normal lifestyle
• Interventions at the individual level:
– Tailor treatment to symptoms; monitor and treat complications
• Interventions at the community/population level:
– Ensure access to treatment (health insurance, local clinics available)
– Protect employees who are out sick from losing jobs
– Research to find better treatments; monitor resistance patterns
41
Levels of Prevention Table
42
Strategy for Prevention
Modify Existing
Intervention
Programs
Evaluate
Intervention
Programs
Apply
Population-Based
Intervention
Programs
Identify
Populations
at High
Disease Risk
(based on demography /
family history,
host factors..)
Assess
Exposure
Conduct
Research on
Mechanisms
(including the study of
genetic susceptibility)
Epidemiology Division
43
Summary
• Disease prevention aims to reduce avoidable
morbidity and premature mortality by reducing
exposure and disease severity, and facilitating recovery
• Disease prevention efforts complement health
promotion efforts
• There are three levels of prevention. They vary in their
target populations, rationales, goals, activities, and
outcome measures
• Pharmacists can be involved in prevention at both the
individual patient and community or population levels.
44
(II) Control
45
Control
• Concept of control:
The term disease control describes ongoing operations
aimed at reducing:
– The incidence of disease
– The duration of disease and consequently the
risk of transmission
– The effects of infection, including both the
physical and psychosocial complications
– The financial burden to the community.
46
• Control activities focus on primary
prevention or secondary prevention, but
most programs combine both.
control
elimination
eradication
47
Disease Elimination
• Between control and eradication, an intermediate
goal has been described, called "regional
elimination"
• The term "elimination" is used to describe
interruption of transmission of disease, as for
example, elimination of measles, polio and
diphtheria from large geographic regions or areas
• Regional elimination is now seen as an important
precursor of eradication
48
Disease Eradication
• Eradication literally means to "tear out by roots".
• It is the process of “Termination of all transmission
of infection by extermination of the infectious agent
through surveillance and containment”.
• Eradication is an absolute process, an "all or none"
phenomenon, restricted to termination of an infection
from the whole world. It implies that disease will no
longer occur in a population.
• To-date, only one disease has been eradicated, that is
smallpox.
49
Monitoring
• Monitoring is "the performance and analysis of
routine measurements aimed at detecting changes
in the environment or health status of population"
(Thus we have monitoring of air pollution, water
quality, growth and nutritional status, etc).
• It also refers to on -going measurement of
performance of a health service or a health
professional, or of the extent to which patients
comply with or adhere to advice from health
professionals.
50
Surveillance
• surveillance means to watch over with great
attention, authority and often with suspicion
• According to another, surveillance is defined as "the
continuous scrutiny (inspection) of the factors that
determine the occurrence and distribution of disease
and other conditions of ill-health"
51
Objectives of Surveillance
• The main objectives of surveillance are:
– (a) to provide information about new and changing trends in
the health status of a population, e.g., morbidity, mortality,
nutritional status or other indicators and environmental
hazards, health practices and other factors that may affect
health
– (b) to provide feed-back which may be expected to modify
the policy and the system itself and lead to redefinition of
objectives, and
– (c) provide timely warning of public health
so that interventions can be mobilized.
disasters
52
Control of infectious diseases (the 4 “C”s
Control
Cases
Contacts
Diagnosis
notification
isolation
observation
disinfection standard
treatment strict
follow up protective
release
Carriers
detection
Community
Epidemiological
Investigation &
containment
53
Evaluation of control
• Evaluation is the process by which results are compared with the
intended objectives, or more simply the assessment of how well
a program is performing.
• Evaluation should always be considered during the planning and
implementation stages of a program or activity.
• Evaluation may be crucial in identifying the health benefits
derived (impact on morbidity, mortality, sequel, patient
satisfaction).
• Evaluation can be useful indentifying performance difficulties.
• Evaluation studies may also be carried out to generate
information for other purposes, e.g., to attract attention to a
problem, extension of control activities, training and patient
management, etc.
54
To summarize
• The goals of medicine are to promote health,
to preserve health, to restore health when it is
impaired, and to minimize suffering and
distress.
• These goals are embodied in the word "prevention"
• Successful prevention depends upon a knowledge of causation, dynamics
of transmission, identification of risk factors and risk groups, availability of
prophylactic or early detection and treatment measures, an organization
for applying these measures to appropriate persons or groups, and
continuous evaluation of and development of procedures applied
• The objective of preventive medicine is to intercept or oppose the "cause"
and thereby the disease process. This epidemiological concept permits the
inclusion of treatment as one of the modes of intervention
55