Lecturer in Public Health, University of Stirling
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New Paper: Origins of Health Inequalities: The Case for Allostatic Load (Comment & Debate)

As part of the Society for Longitudinal and Lifecourse Studies (SLLS), I have got to meet and interact with a great group of researchers interested in the social-to-biological transition over the lifecourse, namely using biomakers and biological pathways to better understand the impacts that our social and economic environments have on our health. In the summer of 2015, I was asked to comment on a paper submitted to to the Society's journal (Longitudinal and Lifecourse Studies) by some of these colleagues (although it was blinded, it was pretty easy to guess roughly where it came from) on 'Allostatic Load as a Measure of Social Embodiment: Conceptual and Empirical Considerations'.

Allostatic Load is a concept that tries to help us understand how our bodies react to stressful stimuli, not just in one physiological system or measure, but across the body by typically measuring and combining several biomarker measures across an array of systems including the cardiovascular, metabolic and inflammatory systems. This concept and measure is important as our bodies are often being challenged by multiple, changing and sometimes stressful environmental conditions that can alter the stability of our physiological systems. Allostasis is an active process where, given these challenges, our bodies attempt to maintain optimal physiological function by altering the operating set points or range (‘moving the goalposts’) of the physiological systems involved in adapting and reacting to these conditions.

One way to understand this is with something like body temperature. Our body temperature is normally at 37°C, with only a very small variation around this. If our temperature starts to move away from this optimal point, we start to feel very unwell, often linked to some kind of infection or illness. But there are other ways out temperature can be tested, like doing exercise or standing outside in the cold. When we start to feel too hot/cold we try and change our behaviour to rectify this, like drinking cold/hot drinks, putting on/taking off clothes or moving location. Our bodies also try to help out too by sweating or shivering, for example. Our bodies simply cannot cope with movement too far away from these optimal set points. This is often referred to as homeostasis. In contrast, allostasis is where we can move away from these set points and are still able to cope pretty well. Think of something like blood pressure. Over our lives, our blood pressure changes. Often we don't even notice until a nurse or doctor tells us that we have high blood pressure. Sometimes your blood pressure will be raised short-term because of 'stress' or diet or simply being awake, for example. However, these short-term changes can be remedied. Our bodies do this because they need to react to changes in our environments. They are adapting to their circumstances, which is a good thing. If however, these daily challenges persist over long spells it becomes harder and harder for the body to return to the way it was before and we can move further and further away from these optimal set points or ranges of 'normalcy'. This is what we call Allostatic Load, where our bodies are almost weighted away from the optimal points for functioning.

So, back to the paper! Basically although the concept is widely accepted in the field, there remain doubts and debates about how to measure it; if it's better than simpler/cheaper concepts/measures; does it help us understand the complex interactions between our environments and our bodies; and can it help us change these inequalities. These are things that I, and the other writers, have raised across five articles. If you're interested in this sort of thing you can find the articles here (subscription need though) or you can request to see the full text.