Paradigm Shift in Public Health: The Re-emergence of Social Determinants

By , 2021-10-08 11:56 下午

The mind is the world. What we do depends on how we see and believe the world, or our paradigm. This is also true for people in the field of public health. Since public health came into being in the nineteenth century, its causal thinking has shifted from the miasma theory to the germ theory, the concept of lifestyle, and recently to the social determinants of health paradigm. In this presentation, I will review the history of paradigm shift in public health, and discuss the future of the social determinants of health paradigm.

The Miasma Theory

The birth of modern public health is an unintended consequence of the industrial revolution. The poor living conditions of workers in the early 19th century gave rise of social medicine and public health. In the beginning, the terms of social medicine and public health were used interchangeably. They studied the social origin of illness and advocated the state’s responsibility for tackling social inequalities in health. Yet, with the defeat of 1848 revolution, social medicine movement came to a quick end, and the broad scope of public health movement was transformed into a more limited program of sanitary reform.

The sanitary reform began in England and spread out in Europe and America. It was based on the “sanitary idea” developed by Edwin Chadwick, the father of modern public health. The sanitary idea consists of three elements: (1) the miasma theory: disease was    caused by unpleasant odors from trash and sewers; (2) public health measure: mainly self-flushing sewers, lined with glazed brick, to remove the unpleasant odors; and (3) Bentham’s utilitarianism: the role of government to realize “the greatest happiness of the greatest number”.

The word “miasma” came from ancient Greek and meant “pollution”. The miasma theory is now discredited. Yet, mortality in England remarkably decreased along with the sanitary reform movement. This was in part due to many of the sources of infectious diseases were removed after cleaning up the environment. But, regretfully, the earlier ideological controversy of health inequalities was reduced to questions of water supplies and sewer lines under sanitary reform.

The Germ Theory

When Koch’s postulates were published in 1890, the miasma theory was seriously challenged by the germ theory. The postulates are: (1) an organism can be found in a host suffering the disease; (2) the organism can be isolated and cultured in the laboratory; (3) the organism causes the same disease when introduced into another host; and (4) the organism can be re-isolated from that host. The germ theory was validated in the late 19th century and is now a cornerstone of modern medicine.

Based on the germ theory, the discovery of penicillin and steroid in the 1940s started the golden age of modern medicine. They changed the everyday practice of medicine, but also offered positive proof of “the possibilities of medical science” that one day apparently insoluble health problems would be overcome. Yet, the medical achievements were coincident with the coming of welfare state reforms in Western Europe. For public health, then, the answer to excess illness and death among the poor was conceived as some form of national health service or national health insurance to increase their access to modern medicine.

The Concept of Lifestyle

However, the epidemic of cancers, cardiovascular diseases and chronic respiratory diseases started quiet suddenly, and by the 1940s the non-communicable diseases had replaced communicable diseases as major killers in most of industrialized countries. Regretfully, modern medicine knew very little about the causes of non-communicable diseases and failed to solve these emerging health problems. As a result, many large-scale prospective epidemiologic studies were conducted coincidently to find out possible causes. While risk factor was coined and “multiple causation” became the cannon of modern epidemiology,  the Hill criteria were applied for causal judgment instead of the germ theory. According to the Hill criteria, a statistical association can be considered as a cause by its consistency, strength, specificity, temporal relationship, and coherence.

Thanks to epidemiologists, we now know many and many risk factors for chronic diseases. For example, major risk factors for coronary heart diseases at least includes: high blood cholesterol, high blood pressure, diabetes, overweight and obesity, smoking, lack of physical activity, stress, and poor diet, in addition to sex, age, and family history. Importantly, risk factors often involve decisions and behaviors of an individual, which together constitute one’s lifestyle. Thus, by 1974 when Marc Lalonde proposed his new health field concept, lifestyle had already been considered as major element of health determinant. The other three elements of the health field concept are: human biology, environment, and health care organization.

To tackle lifestyle risk factors, public health has undertaken behavioral modification and community interventions as critical strategies for health promotion. Yet, the evidence indicates that many community-based health promotion program have had only modest impact. Three major problems were identified. First, too many risk factors to find. Second, individuals have difficulties to change their behavior. Third, we rarely examine and intervene on those forces in the community that cause the problem in the first place.

The Social Determinants of Health

After the first International Conference on Health Promotion was held in Ottawa in 1986, however, the strategies of health promotion shifted from individual behavior orientation to social model approach. The Ottawa Charter lists five action means to achieve the goal of “Health for All”: build healthy policy, create supportive environments, strengthen community action, develop personal skills and reorient health services.

Importantly, the Ottawa conference was built in the progress of the “Health for All” movement, initiated by the WHO under the leadership of Halfdan Mahler in the 1970s. The Health for All movement adopted the strategy of comprehensive primary health care, with an emphasis of grass root participation and intersectoral collaboration. In addition, it also considered economic and social development as fundamental to the fullest attainment of health for all and to the reduction of health inequalities, as documented in the Alma Ata Declaration of 1978.

Regretfully, the “Health for All” movement had been substantially weakened by the restrictive interpretation of “selective primary health care” and by the pressure of neo-liberal economic and health policy since the 1980s. And it was not until J.W. Lee took office as Director General of the WHO in 2003 that the movement became reinvigorated. Two years later, the Director General Lee set up the WHO Commission on Social Determinants of Health with an aim to bring together evidence on what can be done to achieve better and more fairly distributed health worldwide, and to promote a global movement to achieve this.

In August 2008, the final report of the Commission on Social Determinants of Health was presented to the WHO Director General, Margaret Chan. In the launch ceremony, the Director General Chan remarked that “This (CSDH Final Report) ends the debate decisively. Health care is an important determinant of health. Lifestyles are important determinants of health. But, let me emphasize, it is factors in the social environment that determine access to health services and influence lifestyle choices in the first place.” Next year, the 62nd World Health Assembly passed the resolution on reducing health inequalities through action on social determinants of health.

The Future

Now the social determinants of health paradigm has come back. But will it be just a dream or a dream which can be realized? What can we learn from the history of paradigm shift in public health?

* Paper presented at Tokyo Conference on Social Class and Health, University of Tokyo, August 6-7, 2011. 


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