L10 Public Health Public Health

Overview

This lecture frames public health as an inherently complex field, moving from models of holistic health, through the determinants of health in a neighbourhood, to public health problems that behave as complex systems (illustrated with antimicrobial resistance), and finally to fields that sit beyond traditional public health (global, planetary and one health) before naming the defining features of “wicked” problems.

Models of health

• Te Whare Tapa Whā (Sir Mason Durie): a wharenui (meeting house) model with well-being (hauora) at the centre, supported by four dimensions represented as the walls: taha wairua (spiritual), taha hinengaro (mental and emotional), taha tinana (physical), taha whānau (family and social), resting on whenua (land, roots) as the foundation.
• Fonofale model (Fuimaono Karl Pulotu-Endemann): a Samoan fale (house) model with culture as the roof, physical/spiritual/mental/other as supporting pillars, family as the floor, and context, time and environment as the surrounding foundation.
• Both models present health as multidimensional and holistic rather than purely physical.

Determinants of health: the health map

• Barton and Grant’s (2006) health map for the local human habitat arranges determinants as concentric rings moving outward from the individual to the global:
  1. People (age, sex, hereditary factors)
  2. Lifestyle
  3. Community (social capital, networks)
  4. Local economy (wealth creation, working, shopping, moving, learning)
  5. Activities (living, playing, learning)
  6. Built environment (buildings, places, streets, routes)
  7. Natural environment (natural habitats, air/water/land, biodiversity)
  8. Global ecosystem (climate change)
• Inputs from the macro-economy, politics and global forces, and from neighbouring regions, act on the whole system from outside.

Public health objectives

By the end of ELM3, students are expected to appreciate:

1. The importance of a population approach to understanding health and disease.
2. The range of determinants of health, from genetic and individual behaviour to social and political influences.
3. The importance of a range of strategies for controlling health problems, including but not limited to the provision of health care.

A further stated objective is to identify the major problems affecting the health of New Zealanders and the community, professional and political factors that influence health decisions, including the allocation and distribution of health resources.

Complex systems

• A complex system is defined by interacting components where the whole is more than the sum of the parts.
• Examples given: climate, organisms, the human brain, cities, ecosystems, social systems, and most public health issues.

Antimicrobial resistance as a worked example

• Inappropriate use of antibiotics arises from: viral infections (treated inappropriately), wrong doses, wrong duration, over-prescription of new antibiotics, and antibiotic use as animal growth supplements.
• Inappropriate use combines with selective pressure and the genetic plasticity of bacteria to drive antibiotic resistance.
• Separately, crowding, homelessness, poor sanitation, day care centres, hospitals and international travel increase spread, which also feeds resistance.
• Antibiotic resistance combines with poor nutrition, immunosuppression and invasive medical procedures to increase susceptibility to infection and antibiotic usage, which feeds back into inappropriate antibiotic use, forming a feedback loop.
• Epidemiologically, resistance spreads through food animals (sheep, swine, cattle, veal calves, poultry) via feeds, rendering, abattoirs/processing, and food handling/preparation/consumption to humans (hospitalised, community, extended care) and companion animals; farm effluent, sewage and industrial/household antibacterial chemicals also spread resistance via soil, wildlife, rivers, drinking water and aquaculture back to humans and animals (after Linton 1977, modified by Irwin).
• A causal-loop (“systems map”) synthesis (Sarah Mitchell, MPH thesis) groups drivers of antibiotic prescription and resistance into clusters: industry influence/public pressure/political will, antibiotic use in food animals, politics of collaboration, political prioritisation of AMR, structural inequities, chemical co-selection side effects, water quality, hospital infections, AMR in the community, pharmaceutical economics and antibiotic development, international influences, and drivers of antibiotic prescription in humans — all converging on a central “level of AMR in humans” node via feedback loops. [!warning] The individual small variable-node labels within this diagram were too small to read reliably even at rendered resolution, so the underlying variable-level detail is not captured here.
• A related food-water-energy-nutrition systems diagram (shiftN, 2009) shows the same style of interlinkage across politics/governance, science, technology, climate change, the farming system, food security, civil security, socio-cultural factors, transport, the value chain, the food industry, consumers, population size, demographic and economic factors, energy, water, environment, and global trade/transport. [!warning] Fine-grained labels within this diagram were largely illegible even at rendered resolution; only the major domain headings could be confidently read.

Beyond public health

• Global health “places a priority on improving health and achieving equity in health for all people worldwide. Global health emphasises transnational health issues, determinants, and solutions; involves many disciplines within and beyond the health sciences and promotes interdisciplinary collaboration; and is a synthesis of population-based prevention with individual-level clinical care.” (Koplan et al., Lancet 2009)
• Planetary health is “the achievement of the highest attainable standard of health, wellbeing, and equity worldwide through judicious attention to the human systems — political, economic, and social — that shape the future of humanity and the Earth’s natural systems that define the safe environmental limits within which humanity can flourish.” In short, it is the health of human civilisation together with the state of the natural systems it depends on. (Horton et al., Lancet 2014)
• One Health / EcoHealth incorporates human, domestic animal, wildlife and ecosystem health. EcoHealth holds that health and well-being cannot be sustained in a resource-depleted, polluted and socially unstable planet, given the inextricable linkages between the health of all species and their environments.

Wicked problems

A wicked problem (after Rittel and Webber, 1973, via CMU Transition Design) has these defining characteristics:

• Never completely solved.
• Every problem is unique.
• There is no clear problem definition.
• Multi-causal, multi-scalar and inter-connected.
• Multiple stakeholders with conflicting agendas.
• Straddle organisational and disciplinary boundaries.
• Every wicked problem is connected to others.
• Every solution ramifies throughout the system.
• Solutions are not right or wrong, only better or worse.
• Can take a long time to evaluate solutions.

Self-test

1. Name the four dimensions of Te Whare Tapa Whā and what sits at its foundation.
2. List, in order from the individual outward, the eight layers of Barton and Grant’s health map for the local human habitat.
3. What are the three public health objectives students are expected to appreciate by the end of ELM3?
4. Define a complex system and give three examples from the lecture.
5. Describe the feedback loop by which increased susceptibility to infection contributes back to antibiotic resistance.
6. Trace how antimicrobial resistance can spread from food animals to humans via the food chain.
7. Distinguish global health from planetary health.
8. What does the One Health perspective incorporate, and what is the basic tenet of EcoHealth?
9. List five defining characteristics of a wicked problem.
10. Using antimicrobial resistance as an example, explain why public health problems are often better understood as wicked, complex problems than as problems with a single, direct cause.

Answers

Reveal answers

1. Taha wairua (spiritual), taha hinengaro (mental and emotional), taha tinana (physical), and taha whānau (family and social) well-being, all resting on whenua (land, roots) as the foundation, with hauora (well-being) at the centre.
2. People → lifestyle → community → local economy → activities → built environment → natural environment → global ecosystem.
3. (1) The importance of a population approach to understanding health and disease; (2) the range of determinants of health, from genetic and individual behaviour to social and political influences; (3) the importance of a range of strategies for controlling health problems, including but not limited to the provision of health care.
4. A complex system is one with interacting components where the whole is more than the sum of the parts. Examples: climate, organisms, the human brain, cities, ecosystems, social systems, and most public health issues.
5. Antibiotic resistance combines with poor nutrition, immunosuppression and invasive medical procedures to increase susceptibility to infection and antibiotic usage; this increased usage feeds back into inappropriate use of antibiotics, which (with selective pressure and bacterial genetic plasticity) drives further resistance.
6. Food animals (sheep, swine, cattle, veal calves, poultry and other livestock) receive antibiotics in feed; dead stock go to rendering while offal and meat pass through abattoirs/processing plants and food handling/preparation to reach humans (hospitalised, community, extended care) and companion animals. In parallel, farm effluent/manure, sewage and antibacterial chemicals enter soil, wildlife, rivers, drinking water and aquaculture, forming an environmental transmission route back to humans and animals.
7. Global health emphasises transnational health issues, determinants and solutions, drawing on many disciplines to synthesise population-based prevention with individual-level clinical care. Planetary health widens the frame further, to the political, economic and social systems that shape humanity’s future together with the natural systems and environmental limits that human health and civilisation depend on.
8. One Health incorporates human, domestic animal, wildlife and ecosystem health. EcoHealth’s basic tenet is that health and well-being cannot be sustained in a resource-depleted, polluted and socially unstable planet, because the health of all species and their environments is inextricably linked.
9. Any five of: never completely solved; every problem is unique; no clear problem definition; multi-causal, multi-scalar and inter-connected; multiple stakeholders with conflicting agendas; straddle organisational and disciplinary boundaries; connected to other wicked problems; every solution ramifies throughout the system; solutions are better/worse rather than right/wrong; can take a long time to evaluate solutions.
10. Antimicrobial resistance arises from many interacting, feedback-linked drivers (clinical prescribing, agricultural use, sanitation, travel, industry and political pressures, pharmaceutical economics, water quality, structural inequities) rather than one cause, so it has no single fix, involves many stakeholders with different interests, and any intervention ripples through the wider system, matching the definition of a wicked, complex problem rather than a simply solvable one.