Lecture7
Preventive medicine and its importance for
improvement of public health
“Prevention is better then cure”
Concepts of 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". Successful prevention depends upon knowledge of
causation, dynamics of transmission, identification of risk factors
and risk groups, availability of prophylactic or early detection
and treatment measures, as organization for applying these
measures to appropriate persons or groups, and continuous
evaluation of and development of procedures applied.
It is not necessary (although desirable) to know everything about
the natural history of a disease to initiate preventive measures.
Often times, removal or elimination of a single known essential
cause may be sufficient to prevent a disease. The objective of
preventive medicine is to intercept or oppose the "cause" and
thereby the disease process. The epidemiological concept permits
the inclusion of treatment as one of the modes of intervention.
Levels of prevention
In modern day, the concept of prevention has become broad-based. It
has become customary to define prevention in terms of four levels:
•primordial prevention
•primary prevention
•secondary prevention
•tertiary prevention
Primordial prevention
Primordial prevention, a new concept, is receiving special attention
in the prevention of chronic diseases. This is primary prevention in
its purest sense, that is, 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). 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.
Primary prevention
• Primary prevention can be defined as "action taken prior to
the onset of disease, which removes the possibility that a
disease will ever occur". It signifies intervention in the
prepathogenesis phase of a disease or health problem (e.g., low
birth weight) or other departure from health. 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.
• Primary prevention is far more than averting the occurrence of
a disease and prolonging life. 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”. It concerns an individual's attitude towards life and health
and the initiative he takes about positive and responsible
measures for himself, his family and his community.
Primary prevention
The concept of primary prevention is now being applied to the
prevention of chronic diseases such as coronary heart disease,
hypertension and cancer based on elimination or modification of
"risk factors" of disease. 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
Population (mass) strategy:
Another preventive approach is "population strategy" which is
directed at the whole population irrespective of individual 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 socio-economic, behavioral and lifestyle changes.
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.
• Primary prevention is a desirable goal. It is worthwhile to
recall the fact that the industrialized countries succeeded in
eliminating a number of communicable diseases like
cholera, typhoid and dysentery and controlling several
others like plague, leprosy and tuberculosis, not by medical
interventions but mainly by raising the standard of living
(primary prevention). And much of this success came even
before immunization became universal routine. The
application of primary prevention to the prevention of
chronic disease is a recent development. To have an impact
on the population, all the above three approaches
(primordial prevention, population strategy and high-risk
strategy) should be implemented as they are usually
complementary.
Primary prevention
• In summary, primary prevention is a "holistic"
approach. It relies on measures designed to
promote health or to protect against specific
disease "agents" and hazards in the
environment. It utilizes knowledge of the
prepathogenesis phase of disease, embracing the
agent, host and environment. The safety and low
cost of primary prevention justifies its wider
application. Primary prevention has become
increasingly identified with "health education"
and the concept of individual and community
responsibility for health.
Secondary prevention
• Secondary prevention can be 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,
case finding programmers) and adequate treatment. By
early diagnosis 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 have taken
place; and reverse communicability of infectious
diseases. It may also protect others in the community
from acquiring the infection and thus provide at once
secondary prevention for the infected individuals and
primary prevention for their potential contacts.
Secondary prevention
• Secondary prevention is largely the domain of clinical
medicine. The health programmers initiated by governments
are usually at the level of secondary prevention. The
drawback of secondary prevention is that the patient has
already been subject to mental anguish, physical pain; and
the community to loss of productivity. These situations are
not encountered in primary prevention.
• Secondary prevention is an imperfect tool in the control of
transmission of disease. It is often more expensive and less
effective than primary prevention. In the long run, human
health, happiness and useful longevity will be achieved at
far less expense with less suffering through primary
prevention than through secondary prevention.
Tertiary prevention
• When the disease process has advanced beyond its early
stages, it is still possible to accomplish prevention by what
might be called "tertiary prevention". It signifies
intervention in the late pathogenesis phase. Tertiary
prevention can be defined as "all measures available to
reduce or limit impairments and disabilities, minimize
suffering caused by existing departures from good health
and to promote the patient's adjustment to irremediable
conditions". For example, treatment, even if undertaken
late in the natural history of disease may prevent squeal
and limit disability. When defect and disability are more
or less stabilized, rehabilitation may play a preventable
role. Modern rehabilitation includes psychosocial and
medical components based on team work from a variety
of professions. Tertiary prevention extends the concept of
prevention into fields of rehabilitation.
Rehabilitation
• Rehabilitation has been defined as "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". It includes all measures aimed at reducing the
impact of disabling and handicapping conditions and at
enabling the disabled and handicapped to achieve
social integration. Social integration has been defined
as the active participation of disabled and handicapped
people in the mainstream of community life.
• Rehabilitation medicine has emerged in recent years as a
medical speciality. It involves disciplines such as physical
medicine or physiotherapy, occupational therapy, speech
therapy, audiology, psychology, education, social work,
vocational guidance and placement services.
The following areas of concern in rehabilitation
have been identified:
• Medical rehabilitation - restoration of function
• Vocational rehabilitation - restoration of the capacity to earn a
livelihood.
• Social rehabilitation - restoration of family and social relationships
• Psychological rehabilitation - restoration of personal dignity and
confidence.
Rehabilitation is no longer looked upon as an extracurricular
activity of the physician. The current view is that the responsibility of
the doctor does not end when the "temperature touches normal and
stitches are removed". The patient must be restored and retrained
"to live and work within the limits of his disability but to the hilt of
his capacity". As such medical rehabilitation should start very early
in the process of medical treatment.
Examples of rehabilitation are: establishing schools for the blind,
provision of aids for the crippled, reconstructive surgery in leprosy,
muscle re-education and graded exercises in neurological disorders
like polio, change of profession for a more suitable one and
modification of life in general in the case of tuberculosis, cardiac
patients and others. The purpose of rehabilitation is to make
productive people out of nonproductive people.
Preventive medicine
• Preventive medicine developed as a branch of medicine distinct from
public health, based on etiology. It is, by definition, applied to
"healthy" people. It scored seven successes in the prevention of
communicable diseases base on immunization, so much so, in its
early years, preventive medicine was equated with the control of
infectious diseases.
• As concepts of the aetiology of disease changed through time, so too
have the techniques and activities of preventive medicine. Preventive
medicine is no longer concerned, as used to be, with immunization,
important though it may be. The concept of preventive medicine has
broadened to include health promotion, treatment, and prevention of
disability c well as specific protection. Preventive medicine has thus
come to include both specific medical measures (e.g.,
immunization), as well as general health promotional measures (e.g.,
health education). Within this change in the definition and scope of
preventive medicine, it has become clear that promoting health and
preventing illness involve responsibilities and decisions at many
levels - individual, public and private; and that these efforts are
applied to whole population or to segments. In this, preventive
medicine has become akin to public health.
Preventive medicine
• Preventive medicine has become a growing point in
medicine. It has branched into newer areas such as
screening for disease, population control, environmental
control, genetic counseling and prevention of chronic
diseases Community prevention and primordial prevention
are relatively new concepts which are being applied in the
community control of coronary heart disease, hypertension
and cancer with palpable success. The emergence of
preventive pediatrics, preventive geriatrics and preventive
cardiology are relatively new dimensions of prevention.
• Since preventive medicine has increasingly tended to be
applied to the organized health activities of the community,
the term "preventive medicine" is regarded as synonymous
with public health. Both terms often appear in combination
(e.g., Maxcy-Rosenau Textbook of "Public Health and
Preventive Medicine").
Preventive medicine
• Associated with the concept of public health, preventive
medicine has been defined as meaning "not only the
organized activities of the community to prevent
occurrence as well as progression of disease and
disability, mental and physical, but also the timely
application of all means to promote the health of
individuals, and of the community as a whole, including
prophylaxis, health education and similar work done by a
good doctor in looking after individuals and families". In
this the goals of preventive medicine and public health
have become identical, i.e., Health for All. In line with this
extension of the scope of preventive medicine, it is now
customary speak of primary, secondary and tertiary
levels of prevention. The cornerstone of preventive
medicine is, however "primary prevention".
Health education - the important functions of a doctor and
one of the measures to promote general health and wellbeing of the population
• In India, at present, a doctor soon after graduation has often to
take charge of a health centre (population 30,000) which is
usually in a rural area. He is called upon to provide promotive,
preventive, curative, rehabilitative and emergency care services
appropriate to meet the main health problems in the community,
with special attention to vulnerable groups. One of the
important functions of a doctor (physician) must be health
education. The term "doctor" by derivation means to teach.
Therefore the physician has a major responsibility as a teacher
and educator. In his practice, in his professional associations and
in his community activities, the physician has wide educational
opportunities. As a teacher, the physician can play an effective
role in community health education so that individuals, families
and communities assume greater responsibility for their own
health and welfare, including self-care. He can also generate and
mobilize community participation in health programmers
through effective propagation of relevant information.
MODES OF INTERVENTION
• "Intervention" can be defined as any attempt to
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intervene or interrupt the usual sequence in the
development of disease in man. This may be by the
provision of treatment, education, help or social support.
Five modes of intervention have been described which
form a continuum corresponding to the natural history
of any disease. These levels are related to agent, host and
environment. They are:
Health promotion
Specific protection
Early diagnosis and treatment
Disability limitation
Rehabilitation
Health promotion
• Health promotion is "the process of enabling
people to increase control over and to improve
health ". It is not directed against any 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
Environmental modifications:
• A comprehensive approach to health promotion
requires environmental modifications, such as
provision of safe water; installation of sanitary
latrines; control of insects and rodents; improvement
of housing, etc. The history of medicine has shown that
many infectious diseases have been successfully
controlled in western countries through environmental
modifications, even prior to the development of specific
vaccines or chemotherapeutic drugs. Environmental
interventions are non-clinical and do not involve the
physician.
Nutritional interventions: These comprise food
distribution and nutrition improvement of vulnerable
groups; child feeding programmers; food fortification;
nutrition education, etc.
• Lifestyle and behavioral changes: The conventional
public health measures or interventions have not been
successful in making inroads into lifestyle reforms. The
action of prevention in this case, is one of individual and
community responsibility for health, the physician and in
fact each health worker acting as an educator than a
therapist. Health education is a basic element of all health
activity. It is of paramount importance in changing the
views, behavior and habits of people.
Specific protection
• To avoid disease altogether is the ideal but this is
possible only in a limited number of cases. The
following are some of the currently available
interventions aimed at specific protection: (a)
immunization (b) use of specific nutrients (c)
chemoprophylaxis (d) protection against occupational
hazards (e) protection against accidents (f) protection
from carcinogens (g) avoidance of allergens (h) the
control of specific hazards in the general environment,
e.g., air pollution, noise control (i) control of consumer
product quality and safety of foods, drugs, cosmetics,
etc.
Early diagnosis and treatment
• Early detection and treatment are the main interventions
of disease control. The earlier a disease is diagnosed and
treated the better it is from the point of view of
prognosis and preventing the occurrence of further cases
(secondary cases) or any long-term disability. It is like
stamping out the "spark" rather than calling the fire
brigade to put out the fire.
• Strictly speaking, early diagnosis and treatment cannot be
called prevention because the disease has already
commenced in the host. However, since early diagnosis and
treatment intercepts the disease process, it has been included
in the schema of prevention, in as much as the goal of
prevention is "to oppose or intercept a cause to prevent or
dissipate its effect".