Producing Health Consuming Health Care

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In this section we zoom out to a big picture view of the relationship between health and health care. Over the past century or so there have been dramatic improvements in life expectancy at birth mainly due to reduction in deaths due to communicable diseases. There has been an ongoing debate about the role of health care in this improvement and a warning that increasing chronic degenerative diseases will start to shorten lifespan, particularly cardiovascular disease associated with obesity and diabetes. More recently there has be a move to reduce health inequalities within countries by addressing the social determinants of health. Once basic effective health interventions have been fully implemented, social determinants of health may contribute up to 90% of the causative links to illness. The WHO Commission on the Social Determinants of Health, led by Sir Michael Marmot, produced a series of studies, highlighting the need for both action and research here. The distinction between Health and Health Care is also captured in the Institute for Health Improvement’s (IHI) [Triple Aims Program]. They aim to improve the individual patient experience and the health of entire communities, at a reasonable per capita cost. Enhancing the patient experience is addressed in terms of clinical outcomes, safety and satisfaction.

A key paper on the relationship between health and health care is Evans RG, Stoddart GL. Producing health, consuming health care. Soc Sci Med 1990; 31: 1347–1363, and republished in a book edited by Evans Barer and Marmor, Why are some people healthy and others not? the determinants of Health of Populations 1994 Aldine de Gruyter NY. This is sometimes referred to as the Field concept of Health. This paper builds up a series of box and arrow diagrams and uses a thermostat home heating analogy to describe the contribution of healthcare to health. Here we describe the structure and behavior of the thermostat analogy in simple system dynamics computational models. We then show some of the dynamics of health and healthcare described in the paper in computable models rather than diagrams. We then apply simple virtual experiments, with policy options and behavior over time graphs, to elaborate the argument outlined in the paper.

Thermostat Analogy

Thermostat analogy in the paper (on p35 of the book) “A healthcare (heating) system diagnoses disease (like a thermostat detects a fall in air temperature) and responds with treatment (turns on the furnace). External factors are like the temperature outside the house (a very cold night is equivalent to an epidemic. But the consequences of such external events are moderated by the response of the heating/health care system. The thermostat can of course be set at different target temperatures, and the control system of the furnace can be more or less sophisticated depending on the extent and duration of departures from the target temperature.”

Fig. 1 - Thermostat Concept Map [Source]

Applying the thermostat analogy to health care

In their thermostat analogy with health care, Evans and Stoddart compare disease with Room Temperature and the furnace produces healthcare by burning money as fuel (healthcare spending). The target High/Low permissible disease (or health) range differ from the thermostat in the healthcare house. You can have a house too hot, but you can never be too healthy. Indeed the more health you have, the more health you want. Professionally defined needs are adjusted according to the capacity of the health system and pressures on it. There are always unmet needs. Too much care produces iatrogenic disease, side effects, prolonging dying, too little value for too much money on health at the expense of other goals in life that produce wellbeing. Individual perceptions by the worried well grows the industry, with little reduction in disease. Unlike the thermostat there is no stable equilibrium

The systems do differ, insofar as the house temperature can be increased more or less indefinitely by putting more fuel through the furnace (or adding more furnaces). In principle, the expansion of the health system is bounded by the burden of remediable disease. When each individual has received all of the healthcare which might conceivably be of benefit, then all needs have been met, and ‘health’ in the narrow sense of absence of (remediable) disease or injury has been attained. Health is bounded from above, Air temperature is not. The occupants of the house do not want an ever increasing temperature, whether or not it is possible. Too much is as bad as too little. Yet no obvious meaning attaches to the words too healthy. More is always better, a closer approximation to the ideal of perfect, or at least best attainable health. In practice the professionally defined needs for care are themselves adjusted according to the capacity of the health care system, and the pressures on it….As old forms of disease or injury threaten to disappear, new ones are defined. There are always unmet needs.

Too much health care can be iatrogenic disease, the opportunity costs of very small benefits relative to the costs, by foregoing other goals in life before health and excessive anxiety and a sense of dependence on health care (worried well) Unlike a heating system however health care systems do not settle down to a stable equilibrium of temperature maintenance and fuel use. The combination of the ‘ethical’ claim that all needs must be met, and the empirical regularity that, as one is met, another is discovered, apparently ad infinitum, leads to a progressive pressure for expansion in the health care systems of all developed societies. It is as if no temperature level were ever high enough, and more fuel must always be added to the furnace(s). Footnote: If building environmental standards were set by fuel supply companies, would we have similar problems with the regulation of thermostats? …. In terms of the thermostatic model, public discussion still consists almost entirely of claims by providers (with considerable public support) that the room temperature is not high enough, or is in danger of falling, or that a severe cold spell is on the way…but in any case it is imperative that we install more and bigger furnaces immediately, and buy more fuel. Meanwhile payers wring their hands over the fuel bill and seek, with very little external support, ways of making the existing heating system more efficient. The providers of health care, as the owners of fuel supply companies, may give efficiency a lower priority than those who are responsible for paying the bills. But there is a much more fundamental question, The people who live in the building are primarily concerned with the level and stability of the room temperature, not the heating system per se. They become drawn into the exclusive focus on the heating system, if they perceive this is the only way to control the room temperature.”

We can replicate this dynamic by adding a ramp function for the HIGH Heater Setting. Here is the thermostat concept map modified for the analogy.

Fig. 2 - Health Care Spending Thermostat Analogy [Source]

From EBM Diagrams to a computable model

We will attempt to use the set of diagrams in the paper to build an ithink SD model. The big advantage is that it will produce a Behaviour over time graph as output. The big disadvantage is that it requires us to make sure we are consistent in our concepts and units of measure. This is similar to the need to explicitly convert heat into temperature in the thermostat example, but in social systems the calibration remains highly uncertain. Therefore we must heed some old advice.

“It is the mark of an instructed mind to rest satisfied with the degree of precision which the nature of the subject admits and not to seek exactness when only an approximation of the truth is possible.” -Aristotle 384 - 322 B.C.

Initial Diagrams

Steady State Model

Health Spending Thermostat Models

Final Diagrams

Fig. 3 - Bill Braun's version in MapSys from the HPSIG wiki

Health Disparities and Systems Thinking

Questions & Comments to Geoff McDonnell
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