About Allostasis

The past month on Pain Geeks we explored the theme of Defining Health. I ended up curating a month about the allostatic model of health, because, honestly I had an idea of what it was, but realized I hadn’t actually read any papers about it yet. So off I went to scour the internet and came up with two papers plus one humanities piece (check references for the readings).

Here’s what I learned:

The concept of Allostasis is something that is used to describe what is sometimes referred to as “physiological weathering” (Prior 2022). Also known as stress, in its biological representation seen/measured through certain biomarkers. This concept exists as a way to relate stress to the body and to determine how stress, or our body's way of responding to stress, happens.

Stress is always a bit of a vague concept because it is inherently subjective. What is considered a stressor to one may feel imperceptible to another. On the other hand, two people may experience a stressor similarly, however their response to the stressor could be completely different. It could motivate one while devastating the other. But of course stress, or how we perceive it/respond to it changes based on the overall load of stressors we experience in general. For example with physical injuries, we can have one big accident resulting in lots of damage/physical change, or we can have something like a stress fracture which comes from an accumulation of load over time.

Ultimately, the point at which we reach the tipping point, when the load becomes too much, will be so different for everyone. For one person, it might be that they are relentless in their physical pursuit and lack the appropriate recovery time (i.e. sleep/rest/nutrition). The other could take a break from the physical load, but still have too many other stressors in their lives, (i.e. busy job, family, financial issues) inflicting “load” on their overall system, which could tip them over the edge.

Likewise, in the way that stressors are responded to differently by different individuals, the same stressor can also be responded to differently by the same person, at different times, depending on their situation. For example, a night of poor sleep could have a different effect on you whether it’s one night or a series of nights. Circumstances are always in flux which makes it sometimes hard to pin down what the stress factors in our lives might be.

We learned about the “exposome” which is really a fancy way of saying all the environmental impacts (not like the weather, although, I’m sure I could argue for that, now that I live in rainy Amsterdam… ) on a person. Jokes aside though is an important conceptual shift. When we have terminology that helps us conceptualize the bigger picture, like the term “exposome”, we are better able to understand how things fit together. The reality is that we are living organisms, always situated in an environment, with which we are constantly interacting. It would be inconceivable, to think that this doesn’t impact us.

The definition of the exposome according to the CDC is:

“The exposome can be defined as the measure of all the exposures of an individual in a lifetime and how those exposures relate to health. An individual’s exposure begins before birth and includes insults from environmental and occupational sources. Understanding how exposures from our environment, diet, lifestyle, etc. interact with our own unique characteristics such as genetics, physiology, and epigenetics impact our health is how the exposome will be articulated.”

The term is derived from genetic research, which I guess is a play on words (think chromosome), but also interesting because it creates this idea that something outside of us is a part of us. Like an external gene. It’s cool to think about. We know from epigenetic research that we can influence how genes get expressed and a lot of that is about controlling the exposome. I suppose that this is also where things get blurry to think about, and we can start to get confused about what is internal vs. what is external.

One thing that comes up a lot when you start to learn and talk about Allostasis is inevitably the concept of homeostasis. This makes sense since they are fairly similar terms, and can often, mistakenly be used interchangeably. But they are different and it’s important to recognize that. Homeostasis is more about the defined physiological ranges of certain biological processes that our bodies need in order to survive. For example; body temperature, pH levels and oxygen saturation. Stress being a threat to our homeostatic persistence and allostasis is the mechanism to try and preserve that stability.

So basically, allostasis is our organism's ability to achieve stability through change. Our allostatic load changes over time and in different circumstances dependent on a multitude of internal/external factors. It’s not the same as homeostasis, but related to it and when we are in a state of allostatic overload, this is when unwellness/disease/injury and pathophysiology can occur. Thinking about allostasis in a clinical setting can be really useful because it can help open up possibilities for understanding pain in a way that applies to your whole life. Instead of getting stuck trying to find the one cause and becoming frustrated when you can’t find it, it helps you recognize that you are a part of your environment and vice versa. It may not be the easy way of thinking through a situation or a problem, but it can’t certainly reflect a more realistic situation and I believe help you to come up with more realistic solutions.

Hope you enjoyed this blog! Let me know your thoughts on this below.

References:

Fava, G.A., McEwen, B.S., Guidi, J., Gostoli, S., Offidani, E. and Sonino, N. (2019). Clinical characterization of allostatic overload. Psychoneuroendocrinology, 108, pp.94–101. doi:10.1016/j.psyneuen.2019.05.028.

‌Prior, L. (2021). Allostatic Load and Exposure Histories of Disadvantage. International Journal of Environmental Research and Public Health, 18(14), p.7222. doi:10.3390/ijerph18147222.

Humanities Piece Ted Talk: https://www.youtube.com/watch?v=3NjEV064AQ4

McEwen, B.S. and Wingfield, J.C. (2003). The concept of allostasis in biology and biomedicine. Hormones and Behavior, 43(1), pp.2–15. doi:https://doi.org/10.1016/s0018-506x(02)00024-7.