The Comfort Hypothesis

This weekend I went on a two-day camping trip, which afforded me the opportunity to imagine the environment in which our species evolved. And to do a bunch of bitching and whining about all the minor discomforts I experienced in that environment. And that led me to some speculations about whether the extremely comfortable nature of our modern life can disregulate a pain system that was designed to work in a far different world.

The modern world is soft

Our ancestors evolved in an environment without soft beds, couches, pillows, chairs, floors, and roofs. Their world was composed solely of hard jagged things, dirt and pathogens, and scratchy stuff. When they were sleeping, sitting, standing or walking, they were in constant contact with objects that are hard and rough, and often cold, hot, wet, dirty or infested with bugs. This makes a startling contrast with our modern world, which is highly engineered to ensure that every object we touch is soft, smooth and sterile.

This difference became very noticeable to me after a day or two of camping, even though I brought sunscreen, bug spray, clothes from REI, a sleeping bag, pillows and an inflatable bed. So I was not exactly roughing it, but my experience was still far rougher than my modern life. I had bug bites, I was covered with a layer of sweat and dirt, I had scratches from branches while hiking. I know, it's heartbreaking, but I made it through.

As I was summoning the inner strength to perservere, it occurred to me that this constant low grade non-injurious irritation to the skin is actually the natural condition for humans. Which made me wonder whether the complete absence of this stimulus in the modern world can somehow dysregulate the pain system. Part of what gave me this idea was a seemingly related idea called the hygiene hypothesis.

The modern world is sterile

The hygiene hypothesis essentially asks whether the unnaturally clean lifestyles of the modern world are causing problems with our immune systems, which were designed to work in a world full of constant exposure to pathogens.

The immune system is partly composed of an army of cells designed to kill invaders. In order to function optimally, it needs proper training at a young age in the form of exposure to invaders. If it is denied this practice, it will lack essential skills, such as knowing what to attack when, and how much. And perhaps if the army has nothing to do because there are no invading armies to fight, it gets restless and overreacts to the presence of minor irritants, which causes allergies. Or maybe it just gets confused and starts attacking the body, causing autoimmune disease. This is a rough sketch of some very complex ideas, but the logic is simple - the immune system evolved in the presence of constant exposure to pathogens, and therefore removal of this key input can be expected to change its behavior in some way.

The hygiene hypothesis appears to be gaining more and more scientific support, including epidemiological data showing various allergic and autoimmune diseases are more common in sterile environments than more natural environments with more pathogens.

The comfort hypothesis

So if the hygiene hypothesis can explain the modern rise in allergies, autoimmune disease, and the fact that my daughter cannot take peanuts to school, can the "comfort hypothesis" explain the prevalence of chronic pain in our society?

There is some similarity in logic between the two ideas. The pain alarm system evolved in a situation where one of the major players, the skin, was constantly receiving minor amounts of nociceptive input. We know that nociceptive or other sensory input in one area of the body will affect pain levels in other parts of the body. And counterirritation is a technique for pain relief that involves using an externally applied substance, such as capsaicin, to cause irritation and mild inflammation of the skin, for the purpose of relieving pain in other areas, such as muscles or joints.

Is it possible that a radical reduction in the amount of this peripheral low level nociceptive input to the skin can somehow disregulate the pain alarm system, perhaps causing it to focus excess attention in other areas? Maybe this is a contributing factor in the widespread nervous system sensitivity that underlies many chronic pain conditions.

I don't know the answers to these questions and I do not have any real practical recommendations on the basis of my speculations. Except that it's probably a good idea to "rough" it from time to time, so as not to become too "soft." Our perceptions are in many ways relative. Food tastes better when you fast for a while. Company is more welcome after a period of solitude. And my bed feels a lot softer after a camping trip.

What do you think about these ideas? Have you heard someone else propose them in a different form? Let me know in the comments.