You stagger into the hospital after another day of pain searing through your body. What’s the first thing the doctor asks you? “Where does it hurt?”
It’s a natural starting point for diagnosis, but it seems this simple question can actually reveal much more than we might imagine. According to a paper published this week in the journal PLOS ONE, the pain distribution reported by a patient is enough on its own to predict a host of other information – including the pain intensity, impact, and even how well you’ll be faring three months after treatment.
“The distribution of pain in the body is a vital component of pain assessment,” explains the paper. “Using a hierarchical clustering approach with only a patient’s reported pain areas on a digital body map, we found multiple distinct subgroups of patients … [with] significantly different pain intensity, quality, and impact.”
The huge study, which analyzed data from nearly 22,000 chronic pain sufferers over seven pain management clinics, compared patients’ health, pain, and three-month outcomes against the pain body maps they completed at the beginning of their treatment. These body maps consisted of two drawings – the front and back view of a body – split into 74 total regions, and the patients were asked to indicate which of those regions were causing them pain.
The researchers found that chronic pain sufferers broadly fit into nine groups, with a wide variation in features such as pain intensity, impact on the patient’s life, pain quality, and even demographic and medical characteristics. For example, female patients, older patients, and patients insured by Medicaid were all associated with greater pain intensity than other groups. But crucially, they also found that these characteristics could be predicted to a significant degree of accuracy by just one piece of information: the pain map.
“Using an algorithmic approach, we found that how a patient reports the bodily distribution of their chronic pain affects nearly all aspects of the pain experience, including what happens three months later,” the team said in a statement. “This emphasizes that chronic pain is a disease process … [this result] will be important for future developments in diagnosis and personalized pain management.”
But the research didn’t just reveal the value of pain maps for diagnosis. The team was also able to draw some intriguing hypotheses from the data they gathered – particularly concerning the two groups of patients who reported widespread, chronic pain. This was associated with anxiety, depression, sleep disturbance, and impacted physical function, which is all understandable if you’re living your life in constant pain, but the team also noticed something else: the more widespread a patient’s pain is, the more persistent it is. That, they realized, might imply something important about how pain affects the brain.
“[A] case can be made that reports of widespread pain collected with digital pain body maps are diagnostic of pathophysiological changes in pain processing, now termed the disease of ‘nociplastic pain’,” suggests the paper. “Indeed, widespread pain complaints are a central feature of nociplastic pain.”
Even more than this, the study revealed one group – group G, with neck, shoulder and lower back pain – had the worst three-month outcomes of all. Although these patients may appear similar to other groups with localized pain, the team’s algorithmic approach revealed that they in fact share far more pain characteristics with the two widespread pain groups.
“[It] is possible that group G represents a clinically important entity,” the team wrote. “[It] may be an early stage of generalization of chronic pain that would progress into more widespread pain … If group G is an early stage of generalization, then earlier identification may lead to more appropriate treatment, such as that prescribed to patients with widespread pain.”
“We speculate that the poor patient-reported outcomes in [group G] may be due to a failure in identifying this early stage of generalization,” they suggested.
While the study can’t comment on the effectiveness of various therapies – that data simply wasn’t collected – the team nevertheless believe that their findings do have important clinical applications.
“[The] definitive relationship of body map cluster assignment and pain pathophysiology remains to be seen,” the paper cautions, “[and] even within accepted diagnoses lies significant [differences] in patient characteristics.”
However, they say, “given its speed and ease of use for patients, we predict that body map cluster assignment will be a useful component of chronic pain biosignature development.”