The CDC estimates 20% of adult Americans suffer from chronic pain. But in their 2021 study, 58% of Americans responded they’d had constant pain in some area of the body within the last 3 months. It’s higher in those over 65. Add in everyone else who is affected by someone who lives with chronic pain (e.g. a partner, family members, friends, co-worker) there are few untouched.
And the financial impact is debilitating. One study estimates it costs the U.S. $635B dollars a year. Healthcare costs in severe cases increased over $7,000 annually per person. The cost to the workforce is in the billions due to issues with attendance and productivity.
It’s easy to diagnose and see in patients with severely deformed hands, feet or spines. In others it’s more elusive and diffuse. Too often chronic pain exists in the absence of a specific source. “I ache all over, ” is a common refrain. As a result it’s often diminished or denied by healthcare providers. If the work up is negative then the pain can’t be real. Pain suffers know that’s not true and now new research agrees – chronic pain without a clear cut reason is not only very real but a common cause of chronic pain.
Studies proved that even after the inciting event or illness resolved, the pain it had caused continued to persist- but after-the-fact, no markers were left behind to explain why. In this case pain is no longer indicative of an underlying issue, it is the issue. As stated in last week’s post, recent evidence shows chronic pain outlives its origins, progresses and takes on a life of its own, actually rewriting the central nervous system and creating pathological changes to the spinal cord and brain that perpetuates and worsens the pain.
This is because actual changes occur within the central nervous system when it is bombarded with persistent pain signals. Under these conditions the central nervous system itself becomes hyper-sensitized and actually amplifies the pain it’s sensing. In the beginning hypersensitivity following an injury is a self preservation mechanism to allow time for the tissue involved to heal and warn and remind the brain to avoid any further damage. But prolonged sensitivity changes chemical modulators at the site and decreases pain thresholds. The pain itself actually modifies and changes how it’s perceived locally as well as the central nervous system, especially in the brain and spinal cord. It’s called sensitization. Those “sensitized” not only are more susceptible to painful stimuli but sometimes to even normal or light tough. Their pain recedes slower and they feel “echoes” as it recedes. This explains why some can’t pin point exactly where they hurt, they just do.
This neurological compromise is so consistent in chronic pain patients many believe this is the common denominator. The inciting event caused pain, sensitization caused it’s chronicity. Several studies showed those who had already activated their pain pathways e.g. had recent joint surgery, trauma, arthritis, that led to pain were more sensitized to feeling pain elsewhere. In one experiment, participants with chronic pain who pricked their finger in the same place with a needle repeatedly felt a higher sense of pain than those who hadn’t suffered any previous pain. This was reproduced in healthy individuals without underlying complaints. In half of the participants a blood pressure cuff was inflated repeatedly for a second or two until a muscle ache in the thigh was reported. This has been shown to activate the central nervous systems pain pathway. They too felt increased pain when repeatedly pricking their fingers as opposed to participants who’d not had their system primed with the blood pressure cuff. And it didn’t just have a local effect, it also altered how pain was perceived far away from the area involved because the central nervous system had been activated. Any further injury or episode of pain exacerbated the problem.
It’s frighteningly easy to reproduce in the lab with any noxious stimuli that hurts skin, muscles or organs. Its role in fibromyalgia, osteoarthritis, irritable bowel disease, headaches, TMJ, post surgical pain, and neuropathic pain has been well documented. It can be provoked by a something as simple as a muscle ache and worsen without apparent provocation.
So, in summary- recurrent pain activates the central nervous system. Pain then alters the CNS. Prolonged pain makes the central nervous system in some become more sensitive. Any new pain maintains or worsens this hypersensitivity. It is unclear why some develop hypersensitivity or if it’s a long term condition. But it does explain why chronic, debilitating pain can persist in the absence of specific findings. What is known is it hurts. It alters how we live and it’s real. That’s why learning how to live with chronic pain is so important.