Chapter 4. Public Health in Dermatology

Definition

The World Health Organization defines health as “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.”1 The key message of this definition is that health is a holistic measure that is influenced by socioeconomic factors and inequality. Public health is a discipline in which the level of focus is on the health of populations as opposed to that of individuals, as is the case in clinical medicine. A useful definition of public health is as follows:

Public health is the science and the art of preventing disease, prolonging life, and promoting physical health and mental health and efficiency through organized community efforts toward a sanitary environment, the control of community infections, the education of the individual in principles of personal hygiene, the organization of medical and nursing service for the early diagnosis and treatment of disease and the development of the social machinery to ensure to every individual in the community a standard of living adequate for the maintenance of health.2

This definition articulates some of the roles of public health practitioners in relation to society and health. It also highlights the four key areas of public health action: (1) preventing disease and promoting health, (2) improving medical care, (3) promoting health-enhancing behavior, and (4) modifying the environment.3

As early as in the fifth century bc, Hippocrates suggested a clear link between environmental factors and disease states. In more recent centuries, the physician John Snow helped to establish the field of public health during the 1854 London cholera epidemic.4 By carefully counting the number of deaths from cholera according to population denominators in specific London districts, he was able to establish that household water supply might be the key common factor leading to cholera deaths. Snow hypothesized that cholera was a water-borne disease, and he was able to trace the origin of the epidemic to a contaminated water pump in Broad Street, Soho. Consequently, he ordered removal of the pump handle, which was followed by a dramatic reduction in cholera deaths. Thus, Snow first made detailed planned observations, then analyzed the data, formulated a hypothesis, tested this hypothesis through experiment, and finally mounted a campaign to prevent further disease. This led to a widespread political campaigning for clean water from which millions have benefited worldwide ever since. What is intriguing about Snow's work on the causal relationship between water and cholera is that it preceded the discovery of the Vibrio cholerae organism by Koch a third of a century later.

Public health has played a key role in the prevention and treatment of dermatologic diseases. One of the first historical examples is scurvy. In 1746, James Lind discovered through observation, analysis, and performance of a controlled trial that scurvy in sailors was a dietary disease that could be cured by administration of oranges and lemons5 (see eFigs. 4-0.1 and 4-0.2). Lind's treatise preceded the discovery of vitamin C by more than a century. In 1775, Percivall Pott was the first to describe an occupationally induced cancer by noting that the mortality from scrotal cancer was 200 times higher in chimney sweeps than in other workers.6 He attributed the excess mortality to tar and soot exposure in combination with poor personal hygiene. The first carcinogenic polycyclic aromatic hydrocarbon was not discovered until 1933. In the early twentieth century, pellagra was a major public health problem (see eFig. 4-0.3). There were 100,000 deaths from the disease in a 40-year period and over 3 million sufferers in the United States at that time. In 1914, Dr. Joseph Goldberger noticed that inmates at the Georgia State Sanatorium developed high rates of pellagra whereas the nurses and attendants did not, and concluded that the origin of pellagra was probably a disease caused by a dietary deficiency. He confirmed his hypothesis with controlled clinical trials.7 The deficient dietary factor, niacin, was discovered in 1937.

Collectively, these examples illustrate the importance and potential power of public health in the prevention of disease. These examples also highlight the fact that knowledge of disease pathophysiology (i.e., mechanisms) is not always a prerequisite to determining the cause or risk factors for a disease and the potential for effective public health interventions.

Traditionally, dermatology, like other branches of specialist medicine, has concentrated on the treatment of those who have fallen ill, those who believe they are ill, or people at high risk of developing disease. For instance, we prescribe topical corticosteroids for those with atopic dermatitis, and we may give advice on sun protection to patients who previously had a malignant melanoma. We may see such melanoma patients on a regular basis in skin cancer follow-up clinics to monitor treatment success and to be able to detect recurrences or new early second melanomas. Doctors and patients alike tend to be highly motivated when such an approach is used. The potential benefits seem obvious, and although there may be adverse effects associated with the prescribed treatment, such as skin thinning with prolonged use of topical corticosteroids, or a scar from excision of a melanoma, many patients will accept such risks, because appropriate treatment leads to a tangible and significant improvement of symptoms and improved quality of life or survival. Such an approach to tackling disease has often been referred to in the literature as the high-risk approach, because it focuses on the treatment and detection of those at high risk of developing disease and those who have already fallen ill.8

In contrast to the high-risk approach, the ultimate aim of public health medicine and public health dermatology is to prevent the development of disease in the first place whenever possible, not only by forestalling it in those identified as being at high risk (e.g., because of a strong family history), but by shifting the entire distribution of a certain exposure in a healthier direction for the whole population (population strategy). Such a low-risk approach can be implemented through large-scale public health education campaigns aimed at fundamentally changing the entire population's behavior and lifestyle. For example, based on the data of the Framingham study one can extrapolate that a reduction of everybody's blood pressure by 10 mm Hg would result in an overall reduction in mortality from heart disease of around 30%.8 In dermatology, a good example of a such a population strategy is attempts to change the general population's sun exposure behavior to reduce exposure to ultraviolet light and ultimately skin cancer incidence and mortality through public health education campaigns that are national (e.g., Australia) or international (e.g., the World Health Organization's INTERSUN program, http://www.who.int/uv/intersunprogramme/en/) in scope (Fig. 4-1). This makes sense particularly in a country like Australia, because a strong association between ultraviolet radiation and melanocytic and nonmelanocytic skin cancer is well established, and such risk is distributed widely through the predominantly fair-skinned population. Skin cancer is an important cause of death in economically active younger people, and treatments for all forms of skin cancer pose an important burden on many countries’ health care resources. Simple measures, such as avoiding sun exposure during peak hours of radiation and wearing suitable clothing, can provide adequate protection. The state of Victoria, Australia, has the most comprehensive population-based primary prevention campaign against skin cancer in the world (SunSmart campaign, http://www.sunsmart.com.au/), and it has been reported that this program's public investment was worthwhile. Not only has it resulted in a significant reduction in skin cancer incidence and mortality, but the returns from savings on skin cancer treatments have also exceeded the overall costs of the SunSmart campaign.9

In view of the above, it seems obvious that upstream prevention is more desirable than treating sick individuals who come for treatment downstream after a long chain of pathologic events, some of which may be irreversible. However, it is generally more difficult to persuade healthy individuals to protect themselves against prolonged sun exposure than to persuade those who have already had a malignant melanoma excised. Partly because of this, funding for population prevention strategies is often difficult to obtain, yet the whole population will potentially benefit, as long as such interventions are evidence based and sustainable. It is also worth pointing out that although a public health intervention such as vaccination against measles has dramatically reduced the incidence of disease at a population level, it is impossible to say which individuals have been helped by such a population intervention—a phenomenon known as the prevention paradox.

A population strategy is not suitable for trying to control all skin diseases at present, because such a strategy depends on the knowledge of modifiable risk factors. In the many cases for which exposures that predispose to a particular skin condition are unknown, prevention through avoidance is not possible, and the only option available is treatment of disease rather than primary disease prevention.

Balancing Benefit and Harm

Making the conceptual jump from thinking about individual patients to thinking about entire populations can be challenging for practicing dermatologists, especially because such jumps can come up with some surprising results. For example, a dermatologist with an interest in contact dermatitis might see a case of severe hand dermatitis in a printer caused by allergic contact dermatitis from a chemical and then publicize such a case in a respected journal.10 Another dermatologist reading such a case report might come to the conclusion that allergic contact dermatitis is an important cause of hand dermatitis in printers. Yet when this dermatologist visits the workplace to conduct a survey of all cases of hand eczema in printers, it becomes apparent that true allergic contact dermatitis is probably quite rare, and by far the most common cause of hand eczema is constant low-grade exposure to soap and water from repeated washing and friction from paper and dirt.11 Thus, it is possible that a little bit of harm affecting a lot of individuals can add up to much more in absolute terms (the realm of the public health/occupational health physician) than a lot of harm affecting one or two workers (the realm of the dermatologist). Another well-known example of such a phenomenon is the effects of smoking on reduction in cardiovascular disease. Even though the association between tobacco smoking and lung cancer (relative risk of 14.0) is much stronger than that between smoking and cardiovascular disease (relative risk of 1.6), strategies for smoking cessation save around twice as many lives from cardiovascular disease than from lung cancer simply because heart disease is much more common than lung cancer.12 Therefore, from a public health perspective the population-attributable risk (the proportion of the disease that may be attributable to a particular risk factor) is more important than other traditional measures of risk, such as the relative risk (whose magnitude may tell us something about the strength of a particular association). In a study of risk factors for psoriasis in Italy, Naldi et al found that smoking accounted for up to 26% of all cases.13 In individuals with psoriasis who smoked and who also had a family history of psoriasis, an increased body mass index might accounted for up to 48% of disease.13 The fact that smoking and obesity are modifiable risk factors suggests that psoriasis is preventable, at least to some degree, in this population.

So far, we have illustrated the public health approach in dermatology using mainly historical examples. Yet although current dermatologic research is still relatively dominated by the pursuit of studies in which the unit of analysis is at a cellular or subcellular level, there are some good examples of public health dermatology “in action.”

One of the classic studies illustrating the public health approach “in action” for infectious skin disease was that conducted by Taplin and colleagues concerning scabies among Kuna Indians on the San Blas Archipelago.14 These islands off the coast of Panama were plagued by very high rates of scabies in children in the 1980s, which led to misery and secondary bacterial infections. Despite the use of the best treatments available to combat the problem, the population burden of scabies remained largely unchanged. Only after the adoption of a public health approach in which everyone in defined areas was treated did the prevalence of scabies fall dramatically from approximately 33% to approximately 1%. Similar dramatic decreases in scabies prevalence (from 25% to 1%) and in associated pyoderma and possibly poststreptococcal nephritis have been observed through the use of population-based treatment with ivermectin in the Solomon Islands.15 Another example is the Global Alliance to Eliminate Lymphatic Filariasis (GAELF; http://www.filariasis.org/), an alliance between the World Health Organization, ministries of health, and the private sector aimed at the worldwide eradication of this devastating disease by 2020. GAELF is probably the biggest public health program ever and involves mass treatment of around 750 million people in 48 countries with antifilarial drugs and also includes public health education and advice on skin care of lymphedematous legs to prevent further morbidity. Public health interventions are not restricted to administration of pharmaceutical drugs but can also include educational interventions such as the public education campaigns for reducing skin cancer through reduction in ultraviolet light exposure. One such successful program has been the introduction of basic dermatologic care in Mali through the development of a training program for general health care workers on the management of common skin diseases.16 The proportion of patients with skin disease with a clear diagnosis increased from 42% before the training to 81% after it. Although such dramatic effects might be overestimated in a simple before-and-after study, the effects were sustained for up to 18 months after training. Paradoxically, these improvements in care were associated with a 25% reduction in prescription costs, which suggests that inappropriate empirical prescribing was a source of unnecessary expenditure before the training. Other researchers have also documented how scarce family income can be wasted on inappropriate treatment for skin diseases such as pyoderma and scabies in Mexico.17 Ryan has described the role of educational clinics in the prevention of skin cancers as well as the management of early lesions in the albino population of 170,000 in Tanzania.18 The principles of community dermatology in the face of mobile populations are also discussed elsewhere.19

Three further points in relation to public health dermatology are worth noting. The first is that although dermatologists are best placed to provide an accurate diagnosis of skin diseases, such provision may not be realistic for interventions on a public health scale in poorer countries, where there is a strong argument for embedding dermatological skills into primary health care services as has been done successfully in training health care workers in the diagnosis of leprosy in Mali.20 The second is that public health interventions, like drug treatments, are not without their potential drawbacks. For example, limiting sun exposure in order to reduce the incidence of skin cancer may be associated with drawbacks including depression and less skin synthesis of vitamin D, deficiency of which may be associated with a range of diseases such as cancer, bone disease, and heart disease.21 Yet recent studies of seasonal variations in vitamin D levels suggest that the commonly held view that 10 to 20 minutes sun exposure during the summer is enough to boost overall 25 hydroxy Vitamin D levels is wrong, and that sufficient sun exposure for a worthwhile benefit would be countered by an unacceptable burden of skin cancer.22 Therefore, fortifying foods with Vitamin D seems a safer public health option than increasing sun exposure for maintaining adequate vitamin D levels.23 Balancing benefits and harms requires special consideration in public health simply because they affect so many people. Whilst some public health interventions, such as immunization or advice on reduction of sun exposure, allow some degree of choice for individuals to heed or ignore as they choose, others, such as fluoridation of water or addition of iodine to salt, are less amenable to personal modification. Third is that although many public health interventions may not sound as “high tech” as drugs targeted at specific biologic receptors, they may be more effective and appropriate for sick populations. The concept that a little bit of harm affecting a lot of people can add up to more than a lot of harm affecting a few people was developed earlier, but a similar maxim also holds true: sometimes a low-technology beneficial intervention that can be applied to a large population can add up to far greater benefit in population terms than a high-technology solution that will benefit only a few.

Some dermatologists, rather than just viewing the world of skin disease from within the narrow confines of a private practice or hospital-based practice, have already conducted population-based needs assessments for dermatologic care, followed by organization of the appropriate services at a population level. A health care needs assessment conducted in the United Kingdom found that skin diseases are one of the commonest reasons why people consult their family doctor where training was paradoxically the least.24 New data from the World Health Organization project on the Global Burden of Diseases will include important information on the comparative burden of skin diseases compared with other skin diseases (http://www.who.int/healthinfo/global_burden_disease/en/). New methods of communication such as social networking Internet sites have become an increasingly important source of public health information.25

There are increasing international collaborations to try to prevent and reduce the burden of skin diseases at a global level through health care planning and focused interventions. These are carried out through organizations such as the International Foundation for Dermatology (http://www.ifd.org/) in conjunction with the International League of Dermatological Societies (http://web.ilds.org/). The International League of Dermatological Societies is working to improve community dermatologic programs in developing countries, focusing on better diagnosis and clear evidence-based guidance for the management of common dermatoses. Training courses have been established, such as those at the Regional Dermatology Training Centre in Moshi, Tanzania (http://www.global-campus.org/rdtc) and short courses in Guerrero, Mexico, and Mali. One of the key aims of these programs is to educate at the primary care level, with the idea that the trainees will then multiply such knowledge by training others in their own countries. As Weinstock points out in Chapter 1, the burden of skin diseases is high. Many skin diseases such as infections, cancer, and atopic eczema can already benefit from a public health approach. What is needed to redress the relative paucity of public health dermatology is to understand the concept that populations are as important as individuals and to build on the sort of collaboration championed by the International Foundation for Dermatology.