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Preventive medicine 

Preventive medicine
Chapter:
Preventive medicine
Author(s):

David Mant

DOI:
10.1093/med/9780199204854.003.030301

May 31, 2012: This chapter has been re-evaluated and remains up-to-date. No changes have been necessary.

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Essentials

Most deaths before age 80 years are preventable.

Childhood and early adult life

Deaths from infectious diseases and trauma usually reflect poverty and political instability. Prevention requires political action to reduce the risk of war and improve the supply of food, clean water, sanitation, and shelter. Preventive medicine can augment, but not replace, this action by controlling spread of infection through vaccination, health education, control of insect vectors, and treatment of disease carriers to prevent onward transmission.

Middle age

The commonest cause of premature death is vascular disease—mainly heart attacks and stroke. The main causes are obesity, a high-fat diet, and tobacco smoking rather than starvation and lack of clean water. In this context political action is still very important to make it easy for people to take exercise and eat healthily, and to make it difficult for people to buy and smoke tobacco.

Preventive medicine

This can identify and treat people at increased risk of death from vascular disease (particularly those with diabetes, high blood pressure, and high blood lipids) and will save many lives by doing this effectively, but the need for medicines to treat vascular disease in individuals is a measure of public health failure. The coexistence of obesity and starvation as major causes of preventable mortality in many countries is a growing public health challenge. Many effective preventive interventions, such as legislation to make seatbelts compulsory or tax tobacco, should be targeted at the whole population, but preventive medicine provided by clinicians must target individuals. This often requires screening to detect early signs of disease (e.g. HIV infection, cancer) or markers of risk of disease (e.g. high blood pressure, intrauterine growth delay), but clinicians must be clear that something effective can be done to ameliorate the condition detected before any screening is undertaken (see Chapter 3.3.2).

Failure of evidence-based preventive interventions

The usual reason for failure is lack of effective implementation, with the three most important implementation failures being: (1) poor population coverage (only a small proportion of the at-risk population receiving the intervention); (2) inadequate staff training; and (3) inadequate quality control.

Preventive medicine and curative medicine

Preventive medicine is an important and integral part of good curative medicine. All doctors have a responsibility to think about why someone is ill. Whatever disease is diagnosed, the question of whether it could have been prevented, and whether the risk of progression can be reduced, must be addressed. For example, every clinician who diagnoses a stroke must ask themselves whether a previous clinical opportunity to measure and control blood pressure has been missed, and reflect on this in regard to their future practice relating to other patients.

Introduction

In his millennium address, Nelson Mandela reminded the world that ‘we close the century with most people still languishing in poverty, subjected to hunger, preventable disease, illiteracy, and insufficient shelter’. The health gap between rich and poor nations is shameful. For example, life expectancy for men in Sierra Leone is 37 years compared to 79 years in Japan. But even in the economically developed world, many people still die prematurely. In England and Wales, almost 1.4 million years of working life are lost each year due to death before age 65 years. Again, there is a marked gap between rich and poor. Life expectancy at birth is 78 years in men from social class I compared to 68 years in social class V. It is naive to think that medicine will remedy this situation. The fundamental step in achieving good health remains the elimination of poverty, with consequent access to food, sanitation, education, and shelter. But the power of medicine lies in the scientific understanding it provides of the disease process. Preventive medicine uses this understanding both to try to reduce the risk of disease and to detect and treat appropriately emergent disease before it does damage.

What is the scope for prevention? Figure 3.3.1.1 shows the number of women expected to die at different ages if 10 000 were subject to the age-specific death rates in England and Wales of today compared to the 1870s (the pattern is similar for men). The dramatic fall in deaths during childhood and early adulthood demonstrates unequivocally that such deaths are preventable. However, the proportion of men or women who live to over 100 has changed little and remains low (no more than 1%). So there seems to be a reasonable expectation that effective preventive medicine might make death before age 80 years uncommon, but the achievable objective seems to be better quality of life before death, and avoidance of premature death, rather than extension of life beyond what appears to be a maximum span of about 100 years. What preventive medicine cannot offer is immortality.

Fig. 3.3.1.1 Numbers of women dying in United Kingdom at different ages if 10 000 were subject from birth to the mortality rate current in 1871–1880 compared with that in 2003–2005.

Fig. 3.3.1.1
Numbers of women dying in United Kingdom at different ages if 10 000 were subject from birth to the mortality rate current in 1871–1880 compared with that in 2003–2005.

Figure originally drawn by: Doll R. British Medical Journal 1982; 286: 445–53. Source of 2003–5 data: Office of National Statistics Interim Life Tables, United Kingdom.

Preventive strategies

Identifying and reducing risk

The main difference between preventive and curative medicine is the focus on risk. The World Health Organization’s 2002 World Health Report focused on prevention and was entitled Reducing Risks, Promoting Healthy Life. The 10 leading global risk factors for ill health, estimated as together accounting for one-third of deaths worldwide, are shown in Table 3.3.1.1. The most disturbing fact for humanity is the occurrence of both starvation and obesity on the same list. While 170 million children are underweight because of hunger and 3 million each year die from starvation, 300 million adults are clinically obese. Figure 3.3.1.2 shows the impact of the top 20 risk factors according to level of economic development. In developing countries with high mortality, the leading risk factors are hunger, unsafe sex, unsafe water, and nutritional deficiency of iron, vitamin A, iodine, and zinc. In developing countries with low mortality, they are alcohol, blood pressure, tobacco, and (paradoxically) both overweight and underweight. In developed countries they are tobacco, alcohol, blood pressure, cholesterol, and obesity. This overlap in health risk factors between developing and developed countries is a relatively recent phenomenon, creating a double burden of unconquered infection and increasingly unhealthy choices in individual consumption. This often reflects the unacceptable face of marketing in growing free-market economies.

Table 3.3.1.1 Ten leading global risk factors causing a significant burden of disease

Risk factor

Attributable deaths/year (in millions)

Comment

Starvation and hunger

3.4

170 million children (27% of all children <5 years) are underweight

Unsafe sex

2.9

40 million people have HIV, 28 million (70%) in Africa; 99% of AIDS in Africa due to unsafe sex

  • Unsafe water

  • Inadequate sanitation and hygiene

1.7

Most deaths from infectious diarrhoea, 9 out of 10 deaths are in children, virtually all (99.8%) in developing countries

Iron deficiency

1

2 billion people affected; pregnant women and children at highest risk

Indoor smoke from solid fuels

0.8

Half of world population exposed; causes 36% of all LRTI and 22% of all COPD cases

Tobacco consumption

4.9

1 million more deaths attributable to tobacco in 2000 than 1990, mostly due to increased smoking rates in developing countries

Alcohol consumption

1.8

Global alcohol consumption is increasing, most marked in developing countries; 60+ documented detrimental effects outweigh benefit of low to moderate consumption on vascular risk

Obesity

About 5

One billion overweight, 300 m clinically obese; causes 8–15% of life years lost in Europe and North America, less than 3% in Asia and Africa

High blood pressure

7.1

Main modifiable risk factors are diet (especially salt intake), obesity, and lack of exercise

High blood cholesterol

4.4

Mean cholesterol levels vary moderately between WHO regions but never more than 2.0 mmol/litre in any age group

Data from: World Health Report 2002, Reducing Risks, Promoting Healthy Life. World Health Organization, Geneva. www.who.int/whr/2002

Fig. 3.3.1.2 Global burden of disease attributable to 20 leading risk factors in developed and developing countries.

Fig. 3.3.1.2
Global burden of disease attributable to 20 leading risk factors in developed and developing countries.

Reproduced from The World Health Report 2002, with permission from The World Health Organization.

The prevention paradox

Preventive medicine aims to reduce the risk of disease (or the risk of further morbidity and mortality in those who develop disease) so its benefit is the absence of disease in the future rather than the present. Absence of something is a difficult benefit to champion, particularly to the individual. As Geoffrey Rose pointed out many years ago, not only is the benefit intangible but many people must take precautions in order to prevent illness in only a few. Even in a country where diphtheria is common, several hundred children must be immunized to prevent one death. Rose called this the ‘prevention paradox’—a preventive measure, which brings large benefits to the community may offer little to each participating individual.

The risk paradox

One of the three risk factors for cardiovascular disease identified by WHO is a high level of cholesterol in the blood. Figure 3.3.1.3 shows the prevalence of high blood cholesterol in the United Kingdom population, the death rate associated with each cholesterol level, and the proportion of all deaths attributable to cholesterol occurring at each level. The risk paradox is that although those with a blood cholesterol >7.5 mmol/litre are at highest individual risk of disease they account for only 8% of total deaths. The group of people in whom most deaths occur (22%) is that with only a modestly increased cholesterol level of 5.5 to 6.0 mmol/litre. This is simply because of the number of people involved. There are far fewer in the high risk group than in the moderate risk group. Targeting preventive medicine at just the high risk group will often have relatively little impact on the total number of deaths in the population.

Fig. 3.3.1.3 Proportion of coronary heart disease deaths attributable to raised serum cholesterol (percentages above columns). Columns and left axis show population distribution of cholesterol levels. The broken line and left axis show the attributable mortality.

Fig. 3.3.1.3
Proportion of coronary heart disease deaths attributable to raised serum cholesterol (percentages above columns). Columns and left axis show population distribution of cholesterol levels. The broken line and left axis show the attributable mortality.

Reproduced from Rose G. Rose’s Strategy of Preventive Medcine, 2008. With permission from Oxford University Press, Oxford.

Primary and secondary prevention

Use of these terms has changed over time but commonly they can be interpreted as follows:

  • Primary prevention—interventions to reduce the risk of disease in healthy people (e.g. use of seat belts to prevent injury in car accidents; tobacco control to prevent the occurrence of smoking-related disease; immunization against infectious disease)

  • Secondary prevention—interventions to prevent avoidable morbidity in people with disease (e.g. treatment of vascular disease with aspirin; screening for early cancer)

It is immediately obvious that the distinction between primary and secondary prevention is sometimes difficult. Some interventions can fall into more than one category (e.g. stopping smoking reduces the progression as well as onset of many smoking-related diseases) and the definition of disease is not absolute (e.g. many apparently healthy people will have undetected disease). Nevertheless, the pragmatic categorization of preventive interventions into primary and secondary is often useful in practice.

Strategic choices

In choosing priority strategies for risk prevention, the WHO Report recommended that in general it is more effective:

  • to focus on population-based rather than individual interventions

  • to prioritize primary rather than secondary prevention

  • to control distal before proximal risks to health

The recommendation to focus on population rather than individual interventions minimizes the importance of the risk paradox. Taking the cholesterol example, an effective intervention that focuses on reducing dietary fat intake in the whole population not only reduces the number of people at high risk but shifts the entire population distribution of risk to the left. In contrast, the recommendation to prioritize primary prevention aimed at distal risks (i.e. to provide clean water rather than focus on early recognition and treatment of dehydration from diarrhoea) exacerbates the prevention paradox. In public health practice, this may not matter if it is possible to convince the public to accept changes for the public good. However, in everyday clinical practice, individuals are concerned about their own health. It is often easier to persuade individuals to change their behaviour when they see early evidence of disease (e.g. to convince them to stop them smoking after they develop angina). In other words, secondary prevention may be easier to implement than primary prevention.

Defining and identifying the at-risk population

Public and individual interventions

Some public health interventions do not require anything other than a broad geographical definition of risk. Interventions are targeted at whole populations and do not require identification of individuals within that population—for example, road accidents can be reduced by seatbelt legislation and tobacco consumption by taxation without identifying the individual driver or smoker. However, some primary preventive strategies (e.g. vaccination) and most examples of secondary prevention (e.g. screening) have to be delivered to specific individuals at risk. You not only need to know that smokers are at risk, you need to know who smokes. These individuals can be defined in one of three ways: by demographic, phenotypic, or familial characteristics. Within each group of at-risk people so defined, further subpopulations may be identifiable as at particularly high risk.

Demographic risk

This is the most common way to define the target group for preventive-medicine services. For example, the United States Preventive Task Force defines the target group for most of the preventive services it recommends in terms of age. The other demographic risk characteristic used by the Task Force to define the target population is gender. It is obvious why it recommends that breast and cervical cancer screening should only be targeted at women, but gender-specific recommendations are also made for aortic aneurysm (based on differential risk) and gonorrhoea (based on the differential likelihood of asymptomatic infection). Some preventive programmes may target specific ethnic or racial groups—e.g. in Australia, interventions to reduce the risk of rheumatic fever associated with group A streptococcal infection of the throat have been restricted to the indigenous Aboriginal population who are at exceptionally high risk.

Phenotypic risk

A phenotype is a set of observable characteristics of an individual or group. Many epidemiological risk factors for disease are physical characteristics (e.g. obesity, hyperlipidaemia); other phenotypic categories often used to define at-risk target populations are behaviour (e.g. smoking, driving) and disease states (diabetes mellitus, angina). As some phenotypic risks interact (e.g. smoking and exposure to asbestos interactively increase risk of mesothelioma), multiple risk assessment is an increasingly common practice. A number of clinical tools have been developed to help estimate multifactorial risk in everyday practice, such as the New Zealand risk charts for cardiovascular disease.

Familial risk

Recent advances in genetic technology have increased our ability to characterize familial risk accurately, and further advance is likely in the next decade. At present, most preventive medicine programmes in this area use genetic assessment to refine assessment of individual risk in phenotypically identified high risk individuals or families (e.g. cystic fibrosis, neurofibromatosis) or demographically defined populations (e.g. pregnant women at risk of giving birth to a child with Down’s syndrome). However, the characterization of risk based on population-based genetic screening is already technically feasible in the economically developed world, increasing the potential power of preventive medicine but also raising important ethical issues about how society deals with accurate predictions of high disease risk, particularly when evident at or before birth.

Registration, screening, and case-finding

It is much easier to identify specific individuals at risk when universal health registration is in place and its accuracy is systematically maintained. It not only allows efficient provision of primary prevention strategies, such as vaccination, but screening for disease risk is also much more efficient when based on an accurate population register. In the absence of a population health register, it is necessary to rely on case-finding. This requires identification of at-risk individuals during routine clinical work (normally in clinical consultations, but sometimes through contact or family tracing). It is less efficient than systematic population screening, but sometimes provides better access to socially disadvantaged groups who may respond poorly to screening invitations or have no registered address. It also allows some interventions to be given at a particularly appropriate moment (e.g. smoking cessation advice at a consultation for cough or contraceptive advice after termination of pregnancy).

Interventions to modify risk

The importance of public health

The marked improvements in health which have been achieved in economically developed countries over the past 150 years are not attributable to medicine. Life expectancy has doubled mainly because of environmental control of infectious pathogens (through sanitation and control of insect vectors) and a lifestyle that reduces individual susceptibility to infectious disease (better food, shelter, and education). So although medical science can play an important role in guiding public health policy by improving understanding of the mechanisms of disease, and specific medical interventions allow us to treat disease when it occurs, the role of preventive medicine should not be overestimated. In particular, the medical profession should not take upon itself responsibilities for public health, which are more appropriately assumed by governments and other social and environmental agencies.

The preventive responsibilities of all doctors

However, preventive medicine is an important and integral part of good curative medicine. All doctors have a responsibility to think about why someone is ill. Whatever cause is identified (physiological, social, or psychological), the question about whether the cause can be prevented (and the risk of future disease reduced) should be addressed. Clinicians should be held professionally accountable if they can be shown to have missed a previous clinical opportunity to measure blood pressure in an individual who subsequently develops a stroke. Doctors who work in a primary care role (particularly those with a registered population) have the added responsibility to ask themselves whether the risk should be addressed at a population rather than just an individual patient level.

Changing behaviour

Five of the ten leading risk factors for preventable mortality cited above are related to individual behaviour: smoking, diet, exercise, alcohol consumption, and unsafe sex. The most effective way to influence such behaviour is usually through public health policy (see below), but individual practitioners can play an important complementary role. People do listen to their doctors, and a number of clinical trials have shown advice on behaviour modification to be cost-effective, even though the impact may be small (e.g. in most studies only about 1 in 30 smokers given brief advice to stop smoking actually quit). Brief advice is most effective if practical in nature (giving guidance on how change can be achieved) and if backed up by written advice to take home. More intensive interventions may be even more effective but tend to be less cost-effective. In each case, it is important to take account of the scientific evidence about effectiveness and the local socioeconomic context.

Immunization

Vaccination is a very effective preventive strategy. Vaccination against smallpox has led to global eradication of the disease; eradication of polio seems a feasible global objective in the next decade. Vaccination against many diseases, particularly diseases of childhood such as measles, diphtheria, and polio, has led to rapid and dramatic falls in disease incidence. Figure 3.3.1.4 shows the impact of introduction of the Hib vaccine in 1992 on the incidence of Haemophilus influenzae infection in England and Wales. Table 3.3.1.2 shows the current routine vaccine schedule in the United Kingdom. Every individual in the population is vaccinated against 11 different organisms, 10 during childhood and 1 in old age. At-risk groups may be required to have specific vaccines to protect themselves (e.g. health workers against hepatitis B), and the general population and travellers to other countries can choose and pay for a range of vaccines for other diseases including hepatitis A, typhoid, and rabies. So the average person in the United Kingdom is now likely to receive vaccination against about 15 microorganisms during their lifetime.

Fig. 3.3.1.4 Effect of introduction of Haemophilus influenzae type b (Hib) vaccination in the United Kingdom on laboratory reports of Hib infection.

Fig. 3.3.1.4
Effect of introduction of Haemophilus influenzae type b (Hib) vaccination in the United Kingdom on laboratory reports of Hib infection.

Reproduced by permission of the Controller, Her Majesty’s Stationery Office.

Table 3.3.1.2 Routine immunization programme in the United Kingdom according to age

2 months

3 months

4 months

12–13 months

3–5 years

13–18 years

65 years+

At-risk groups

Diphtheria

Tetanus

Polio

Pertussis

Haemophilus influenzae B

Meningococcus C

Measles

Mumps

Rubella

Pneumococcus

Influenza

TB

Hepatitis B

Data from: UK Joint Committee on Vaccination and Immunisation (2006). Immunisation against infectious disease. Report of UK Joint Committee on Vaccination and Immunisation. HMSO, London. www.dh.gov.uk/Policy and Guidance/HealthandSocialCareTopics/GreenBook/fs/en

A number of new and important vaccines are on the horizon, e.g. against malaria. But the existence of an effective vaccine does not guarantee the success of an immunization programme. This depends on the effective delivery of the vaccine to the at-risk population. Programmes are often limited in their effect by affordability (many vaccines are too expensive for developing countries), acceptability (parental anxiety about the adverse effects of pertussis vaccine has limited its uptake in many countries), and deliverability (vaccines may lose potency if stored outside a refrigerator). There are also potential problems with the antigenic variability of organisms (e.g. influenza) and the difficulty of immunizing at an age young enough to prevent morbidity but old enough to stimulate an immune response (e.g. measles). Nevertheless, immunization is probably the most important medical contribution to primary disease prevention.

Screening

The issue of screening is dealt with in Chapter 3.3.2. Three-quarters of the preventive services for adults recommended for implementation by the United States Preventive Services Task Force involve screening. The purpose of screening is to identify disease at an early and curable stage. The most important criterion that has to be met for screening to be ethical is that the condition identified can be ameliorated and cured. Good intention is not enough. Screening will do harm if it identifies conditions that cannot be ameliorated, either because of lack of effective interventions or lack of resources. It is particularly important to assess the effectiveness of screening interventions in randomized trials, as people whose disease was detected by screening will appear to clinicians to do well even if the screening is ineffective. This is because early diagnosis will lead to longer survival irrespective of treatment, and illness detected by screening will always tend to be more benign in its natural history than illness detected clinically.

Prophylactic treatment

Although most people think of medicines as cures for current illness, many medicines are prescribed with a view to preventing future illness. Antibiotics are given before surgery to prevent postoperative infection, antimalarials to prevent malaria in travellers, anticoagulants to prevent stroke in people with atrial fibrillation, and lipid-lowering agents to prevent heart attacks in people at high risk of cardiovascular disease. The duration of treatment may also be extended beyond the initial treatment phase to achieve a preventive effect. Antidepressants are continued after cure to prevent relapse, acetylcholinesterase inhibitors to prevent worsening of ventricular dysfunction, and uricosuric agents to prevent further episodes of gout.

It must be clear from these examples that many, perhaps most, drugs have the potential to be used for prevention as well as cure. In some cases (e.g. treatment of diabetes) the distinction between prevention and cure is unhelpful: treatment aims to prevent morbidity in both the short and long terms. However, in all the examples given, prescribing is limited to a defined high-risk group. Prophylactic treatment with drugs is less helpful when a high-risk population cannot be easily defined. It is almost always inappropriate to use prophylactic treatment to reduce population risk for three reasons: the strategy is seldom cost-effective, increasing the reliance of the population on medicine is an adverse social outcome, and uncommon adverse effects can easily outweigh any benefit.

Environmental change

Most environmental causes of disease are best modified on a public health rather than an individual basis. Such factors include the safety of the workplace, environmental pollution, transport safety, food hygiene, and provision of clean water. However, a number of diseases have environmental causes, which need to be recognized and avoided by the individual patient. On a global scale, avoidance of insect and other disease vectors (e.g. by netting) and attention to nutritional hygiene (e.g. by filtering water) are probably the most important. In economically developed countries, the most common diseases amenable to individual environmental intervention are those associated with atopy, such as asthma and eczema. Not all patients have an identifiable allergenic cause for their symptoms and, even if one is identified, avoidance (e.g. of house dust mite in asthma) may not be easy. But dramatic improvement can occur, and treating contact dermatitis without giving advice on contact avoidance, or treating louse bites without giving advice on how to rid clothes of lice, is bad medical practice.

What interventions work?

Public health interventions

It is impossible to list here all the public health initiatives that are known to be effective. There is no doubt that provision of clean water and sanitation; avoidance of war; progressive taxation; provision of education; fiscal policy to reduce tobacco and alcohol use; food policies to reduce community intake of salt, saturated fat, and excess calories; and education to promote safe sex, are all effective public health interventions. Their effective implementation depends on political will at a national and international level. In general, the effectiveness of public health interventions will reflect government attitude to regulation (e.g. whether the presumption of market-led development and free trade dominates individual and societal health concerns) and the understanding of health risk by the general public, politicians, and health practitioners. At an international level, the World Health Organization cites the Framework Convention for Tobacco Control as an exemplar of a very effective government-led international public health initiative. This covers advertising, regulation, taxation, and smoke-free zones as well as the individual treatment of addiction.

Individual interventions

As with public health interventions, it is impossible to list here all the preventive interventions targeted at individuals, which have been shown to be effective. Many are in any case better seen as part of good routine clinical care (and are included in the relevant chapters on specific diseases). Nevertheless, it is worth listing preventive interventions, which may not be included elsewhere, and for which there is very good evidence of effectiveness from clinical trials. One accessible source of regularly updated evidence on individual interventions is the United States Preventive Services Task Force and Table 3.3.1.3 lists the 20 conditions for which evidence of effectiveness is rated by them as A (‘strong’) or B (‘at least fair’). The preventive interventions (other than vaccination) for two important at-risk groups—pregnant women and children—for which there is a similar level of evidence of effectiveness are listed separately in Table 3.3.1.4. Omission of interventions from these lists does not imply that they are unimportant or do not work, but it often implies lack of high-quality research evidence.

Table 3.3.1.3 Preventive interventions recommended for adults by the United States Preventive Services Task Force as providing important health benefit on the basis of research evidence rated as A (strong) or B (fair)

Medical problem

Men

Women

Target groups

Screening interventions

Alcohol misuse

Aortic aneurysm

Once age 65–75 in ever smokers

Breast cancer

Age 40+ (mammography); familial risk (genetic testing)

Cervical cancer

Ever sexually active

Chlamydia infection

Sexually active age <25 years or other at risk groups

Colorectal cancer

Age 50+

Depression

Diabetes mellitus

Adults with hypertension or hyperlipidaemia

Gonorrhoea infection

At risk groups

High blood pressure

HIV infection

At risk groups

Lipid disorders

Men 35+, women 45+; younger if high CVD risk

Obesity

Osteoporosis

Women 60+

Syphilis infection

At risk groups

Other interventions

Aspirin

Adults at increased CVD risk

Breastfeeding promotion

Pregnant and recently delivered women

Breast cancer chemoprevention

Women at high risk of breast cancer

Dietary counselling

Adults at high risk of CVD

Tobacco use counselling

All who use tobacco

Data from : The Guide to Clinical Preventive Services 2006, Recommendations of the U.S. Preventive Services Task Force. US Department of Health and Human Services, Washington, DC. www.ahrq.gov/clinic/pocketgd.pdf

Table 3.3.1.4 Preventive interventions for pregnant women and children (other than vaccination) recommended by the US Preventive Services Task Force as providing important health benefit on the basis of research evidence rated as A (strong) or B (fair)

Recommendation

Children

Pregnant women

Alcohol misuse

Asymptomatic bacteriuria screening

Breast-feeding promotion

Gonococcal ophthalmia neonatorum prophylaxis (antibiotic drops)

Infection screening (chlamydia, gonorrhoea, HepB, HIV, syphilis)

Rhesus (D)-incompatibility screening

Tobacco-use counselling

Visual-impairment screening

Data from : The Guide to Clinical Preventive Services 2006, Recommendations of the U.S. Preventive Services Task Force. US Department of Health and Human Services, Washington, DC. www.ahrq.gov/clinic/pocketgd.pdf

Implementation issues

Cultural constraints

Most behaviour aimed at preventing disease has a strong sociocultural component and reflects prevalent attitudes and norms in society. Preventive interventions are severely constrained by this social context. Convincing people to stop smoking, eat less salt, drink less beer, or drive more slowly is difficult if everyone else is doing the opposite. For example, Fig. 3.3.1.5 shows that the mean blood cholesterol level in Finland is almost twice that in Japan. Migrant studies show that this difference is dietary rather than genetic in origin and so medical advice to reduce fat consumption has the potential to reduce blood cholesterol level from the high level in Finland to the low level in Japan. However, even in clinical trials, dietary advice from health professionals in a community setting seldom achieves a reduction in blood cholesterol of more than 3 to 5%. Studies of salt restriction (to lower blood pressure) show a similar result. Intensive intervention and support is needed for an individual patient to achieve a physiologically significant reduction in intake and many find such a diet unpalatable. Countercultural change is difficult to achieve. The adverse consequence is the common use of medication (in this case statins) to treat what is effectively a sociocultural problem.

Fig. 3.3.1.5 Distribution of serum cholesterol in southern Japan and eastern Finland.

Fig. 3.3.1.5
Distribution of serum cholesterol in southern Japan and eastern Finland.

Reproduced from Rose G. Rose’s Strategy of Preventive Medecine, 2008. With permission from Oxford University Press, Oxford.

Time constraints

Things change over time. The North Karelia project was a large-scale, long-term programme to reduce mortality from cardiovascular disease in northern Finland, started in 1972, which involved both public health and individual intervention. Figure 3.3.1.6 compares mortality from cardiovascular disease in North Karelia with that in 10 other provinces in Finland before and during the intervention by plotting two regression lines. The difference in slopes of these two lines shows that the intervention was to some extent effective. However, far more impressive in magnitude is the absolute fall in mortality over time both in North Karelia and in the other provinces. The lessons for preventive medicine are twofold: the effect of medical intervention may be small compared to the effect of other economic and social influences; and the change in baseline risk and social context over time may be so rapid that it will substantially influence the absolute benefit of any preventive intervention.

Fig. 3.3.1.6 The North Karelia project. Age-standardized annual mortality from cardiovascular disease in men aged 35–64 years in Finland, 1969–82.

Fig. 3.3.1.6
The North Karelia project. Age-standardized annual mortality from cardiovascular disease in men aged 35–64 years in Finland, 1969–82.

Redrawn from original data published by Tuomilehto J et al, British Medical Journal 1986:293:1068–71.

Programme effectiveness

Many of the interventions cited earlier are known to work because they have been tested in clinical trials. However, clinical trials are often done in settings far removed from everyday life. Participants are compliant, those delivering the intervention are highly trained, the technology is of high specification, and quality control is rigorous. These conditions will not hold under ordinary working conditions. When recommended preventive interventions fail, the most common reason is lack of effective implementation of the programme, rather than lack of effectiveness of the intervention itself.

The importance of considering programme effectiveness is seen most vividly in immunization and screening programmes. The three most important issues that determine programme effectiveness are the following:

  • Coverage—What proportion of the population at risk receives the intervention?

  • Delivery—Are factors that affect the delivery of the intervention (like the maintenance of equipment, the training of staff, and the storage of biological materials) up to scratch?

  • Quality control—Are standards set and monitored for key indicators of the intervention process (e.g. immune response or predictive value of screening)?

Failure in just one of these areas in the United Kingdom has damaged programmes promoting immunization (e.g. the resurgence of pertussis after media publicity about potential adverse effects of the vaccine led to a fall in uptake) and cervical screening (e.g. lack of quality control in cervical sampling and cytological assessment led to false negative results and avoidable mortality).

Conclusion

Preventive medicine is an integral part of clinical practice for all doctors. It is our responsibility as clinicians not only to cure the presenting illness but also to take action where possible to prevent future morbidity. However, we must display both humility and assertiveness in our approach. We need to be humble in our approach to patients and to recognize that medicine is not the main determinant of health. At the same time we must display assertiveness in our advocacy of prevention. In the United Kingdom, the Royal College of Physicians’ reports, the campaigning of medical charities, and the decision by virtually all doctors to stop smoking have all played an important part in influencing both public and political opinion against tobacco use. As a profession, we can make a unique and powerful contribution to the prevention of premature death by identifying and publicizing the existence and causes of ill health. We also have a unique and powerful responsibility to act as advocates for our patients in ensuring that these causes are addressed and the risk to their health is ameliorated. Good clinical practice entails preventive medicine, but good preventive medicine is more than just good clinical practice.

Further reading

Rose G (1992). The strategy of preventive medicine. Oxford University Press, Oxford. [The definitive text on the theory of preventive medicine—short, readable, brilliant.]Find this resource:

    UK Joint Committee on Vaccination and Immunisation (2006). Immunisation against infectious disease. Report of UK Joint Committee on Vaccination and Immunisation. HMSO, London. http://www.dh.gov.uk/en/Publichealth/Healthprotection/Immunisation/Greenbook/DH_4097254 [Annually updated short publication which provides a practical, but evidence based, summary of immunization recommendations in the United Kingdom.]Find this resource:

      US Preventive Services Task Force (2006). Guide to clinical preventive services—recommendations of the US Preventive Services Task Force. US Department of Health and Human Services, Washington, DC. http://www.ahrq.gov/clinic/pocketgd.pdf [Summary of current evidence on the effectiveness of preventive health care.]Find this resource:

        World Health Organization (2003). World Health Report 2002. Reducing risks, promoting healthy life. World Health Organization, Geneva. http://www.who.int/whr/2002 [Summary of the main global challenges to preventive health care; chapter 4 quantifies the major risk to health.]Find this resource: