Part 1 - Theory: Thinking About Health

Chapter 4: Basic Concepts in Prevention, Surveillance, and Health Promotion

The stages of prevention

Chapter 1 illustrated how the development of any disease in a patient progresses through a natural history that can, for convenience, be broken into a series of stages. Preventive measures can be applied at any stage along the natural history of a disease, with the goal of preventing further progression of the condition (see PreventionPreventiondisease prevention covers actions to prevent the occurrence of disease, such as risk factor reduction, and also to arrest its progress and reduce its consequences once established. in Glossary). For the purposes of introduction it is convenient to think of preventive actions in terms four main stages, but in reality the stages blur one into the next.

Primordial prevention consists of actions to minimize future hazards to health and hence inhibit the establishment factors (environmental, economic, social, behavioural, cultural) known to increase the risk of disease.2 It addresses broad health determinants rather than preventing personal exposure to risk factors, which is the goal of primary prevention. Thus, outlawing alcohol in certain countries would represent primordial prevention, whereas a campaign against drinking and would be an example of primary prevention.

Examples of primordial include improving sanitation (such that exposure to infectious agents does not occur), establishing healthy communities, promoting a healthy lifestyle in childhood (for example, through prenatal nutrition programs and supporting early childhood development programmes), or developing green energy approaches. Starfield et al. give more examples.2 So, in preventing Catherine Richards’s diabetes, subsidized fitness programmes at the sports centre could have made make such activities more affordable for women like her, and could help to make exercise a norm for women in her community. Similarly, increasing sports programmes in schools may help reduce obesity in the subsequent generations.3 As these are all population-level programmes, primordial prevention is conceptually linked to population health and health promotion, but clinicians can play a role bringing problems to notice and advocating for action on determinants.

Healthy communities. …
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Healthy communities.

During the early 1980s the European regional office of the World Health Organization (WHO) proposed actions to improve the quality of life in cities by making the urban environment conducive to healthy living: providing recreational resources, improved transportation, cleaner environments, more pleasant housing and so on. Toronto was an early participant in the healthy cities movement.4

Primary prevention seeks to prevent the onset of specific diseases via risk reduction: by altering behaviours or exposures that can lead to disease, or by enhancing resistance to the effects of exposure to a disease agent. Examples include smoking cessation and vaccination. Primary prevention reduces the incidence of disease by addressing disease risk factors or by enhancing resistance. Some approaches involve active participation, as with regular tooth brushing and flossing to prevent dental caries. Other approaches are passive: adding fluoride to the municipal drinking water to harden tooth enamel and prevent caries. Primary prevention generally targets specific causes and risk factors for specific diseases, but may also aim to promote healthy behaviours, improve host resistance, and foster safe environments that reduce the risk of disease, for instance, thorough cleaning of operating rooms to prevent post-operative infection. Preventive efforts can be fitted into the agent-host-environment model of causation introduced in Chapter 2.

Secondary preventionSecondary preventionpreventing the establishment or progression of a disease once a person has been exposed to it. Examples include early detection via screening procedures that detect disease at an early stage when intervention may be more cost-effective. includes procedures that detect and treat pre-clinical pathological changes and thereby control disease progression. Screening procedures (such as mammography to detect early stage breast cancer) are often the first step, leading to early interventions that are more cost effective than intervening once symptoms appear. Routine blood sugar testing for people over 40 would be an example relevant to detecting Catherine’s diabetes early. Screening is usually undertaken by health professionals, either at the level of individual doctor-patient encounters (e.g., routine blood pressure checks) or via public health screening programs (e.g., mammography screening). The criteria for implementing a screening programme are described in Part 3.

Once a disease has developed and has been treated in its acute clinical phase, tertiary prevention seeks to soften the impact caused by the disease on the patient’s function, longevity, and quality of life. Examples include cardiac rehabilitation following a myocardial infarction, seeking to alter behaviours to reduce the likelihood of a reinfaction. Tertiary prevention can include modifying risk factors, such as assisting a cardiac patient to lose weight, or making environmental modifications to reduce an asthmatic patient’s exposure to allergens. In the example of Catherine Richards, it might include ensuring regular check-ups to monitor her condition, including eye exams to check for possible adverse outcomes of her diabetes. Where the condition is not reversible, tertiary prevention focuses on rehabilitation, assisting the patient to accommodate to his disability. For reversible conditions, such as many types of heart disease, tertiary prevention will reduce the population prevalence, whereas for incurable conditions it may increase prevalence if it prolongs survival. The key goal for tertiary prevention is to enhance quality of life.

Table 4.1illustrates the primary, secondary and tertiary levels of prevention.

Table 4.1: Examples of primary, secondary, and tertiary prevention interventions targeting individuals and populations

Disease

Intervention level

Primary

Secondary

Tertiary

Colorectal cancer

Individual

Counselling on healthy lifestyles: dietary counselling for people at risk of colorectal cancer, etc.

Hemoccult stool testing to detect colorectal cancer early

Follow-up exams to identify recurrence or metastatic disease: physical examination, liver enzyme tests, chest x-rays, etc.

Population

Publicity campaigns alerting the public to the benefits of lifestyle changes in preventing colorectal cancers; promotion of high fibre diets; subsidies to help people access exercise programmes; anti-smoking campaigns

Organized colonoscopy screening programs

Implementation of health services organizational models that improve access to high-quality care

Infectious diseases: hepatitis C

Individual

Counselling on safe drug use to prevent hepatitis C virus (HCV) transmission; counselling on safer sex

Screening for HCV infection of patients with a history of injection drug use

HCV therapy to cure infection and prevent transmission

Population

HCV prevention includes safer sex practices, programmes to discourage needle sharing among intravenous drug users, etc.

Establish a universal testing system for HCV in high risk groups

(Similar to primary prevention): ensuring close control of high risk sites such as tattoo parlours that have been associated with outbreaks

Metabolic syndrome

Individual

Nutrition and exercise counselling

Screening for diabetes

Referral to cardiac rehabilitation clinics

Population

Built environment favourable for active transport (walking, bicycling rather than using a car)

Community level weight loss and exercise programs to control metabolic syndrome

Implementation of multidisciplinary clinics

Beware: you may see the t…
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Beware: you may see the term secondary prevention mistakenly used in reference (for example) to preventing a second stroke in a patient who has had a first one. This is incorrect, for it would be an example of tertiary prevention, in terms of preventing further damage to the patient’s vascular system.

Bodies in the river A …
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Bodies in the river

A passer-by sees a body floating down a river and calls 911. Firemen arrive and haul the person out. Paramedics start resuscitation and rush the victim to the ER, where the hospital public relations office announces that while everything possible was done to save the victim, sadly he died. Suicide is presumed.

Some time later a similar event happens again. Sensing an ideal political opportunity, the local member of parliament lobbies the Ministry of Health to have an ambulance station built nearby, complete with advanced rescue equipment and special resuscitation training "so that this tragedy need never happen again in our community." A journalist at the press conference pointedly asked why nets or fences could not be installed on the bridge located upstream as this would be more effective and cheaper than maintaining services downstream; he was promptly escorted away from the meeting by the politician’s aides.

Applying the metaphor of ‘upstream’ and ‘downstream’ interventions that was introduced in Chapter 2 to the case of the bodies in the river, tertiary prevention would imply downstream efforts at resuscitation at the scene and in hospital. But of course these may be judged as being "too little, too late." Secondary prevention activities might focus (metaphorically) further upstream and include attempts to identify suicidal people before they make an attempt, perhaps via screening for depression in primary care practices using a brief screen for depressive symptoms. Those who give indications of depression could be more fully evaluated, perhaps by referral to a psychologist. The success of secondary prevention would depend on many factors but the current evidence suggests that it is not effective in preventing suicide. Therefore, primary or primordial prevention may be more effective in this instance. Primary prevention might include social programs for high-risk youth in areas of high suicide rates, or putting up safety nets to prevent the act of suicide. Primordial prevention falls in the domain of population health approaches; these involve a wide range of government agencies and focus on developing healthy public policies and altering underlying determinants of health. Applied to the bodies in the river, primordial prevention would likely focus on the social ecology of suicide, seeking to identify underlying determinants that explain why people in that area are throwing themselves into the river. Is there, for example, a connection between the world economic downturn, local unemployment, debt and feelings of despair? Do such problems occur more commonly in small, one-industry towns in Canada?

More on the stages of …
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More on the stages of prevention

Thinking of prevention as a series of stages offers a useful introduction to the topic, but classifying a given action into a stage may not be simple and depends greatly on the context. On closer examination, you can only take the idea of stages of prevention so far.

For example, checking (and then controlling) blood pressure may represent primary prevention if the condition you aim to prevent is a heart attack. But it may be seen as secondary prevention if the patient has a family history of hypertension and you are screening for this—it may even be tertiary prevention if the patient has already had a heart attack and the goal is to prevent a recurrence. Bother!

Secondary prevention has been defined as slowing the progression of a disease or its sequelae at any point after its inception. From this perspective, treating a disease can be seen as prevention if it slows the progression of the disease or prevents sequelae. In an interview aired on CBC on 19 July 2010, Michel Kazatchkine, Executive Director of the Global Fund to fight AIDS, TB and Malaria, noted that treatment of HIV/AIDS can qualify as primary prevention because it reduces the risk of transmission of the virus.

Conversely, excess use of antibiotics may be viewed as the opposite of prevention if it contributes to the development of resistant organisms. Clinicians should always weigh the costs and benefits of treating against those of not treating in much the same way as they do in prevention. Reflecting this theme, you may also hear the term ‘quaternary prevention’: where a patient is at risk of over-medication, quaternary prevention protects them from new medical invasion, suggesting interventions which are ethically acceptable, and assuring quality of the care process.5


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