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Most of us – an estimated 8 out of 10 people in the United States – will experience back pain at some point in our lives, and the number of people who describe their pain as chronic has been on the rise for years.
Although it comes as no surprise to those who have experienced it, chronic pain can lead to increased irritability, among other issues. But what about heightened sensitivity to lights, sounds, touch?
A new study published in Annals of Neurology found that people with chronic back pain process sounds, especially ones that are unpleasant, more intensely than people without pain. (In the study, participants listened to noises such as “knife scraping glass bottle,” which you can hear by clicking below.) The research suggests that, more generally, their brains tend to amplify unpleasant sensory information – not just pain, the authors said.
There may be “a shared volume knob in the brain that modulates both back pain intensity and sound unpleasantness,” said Yoni K. Ashar, co-director of the Pain Science Program at the University of Colorado Anschutz School of Medicine and senior author of the study. Though, he added, more research is needed.
The facts
People with chronic back pain reacted more strongly to unpleasant sounds than 84 percent of people without pain, the authors said.
The degree of unpleasantness reported in response to noxious sounds was associated with the severity of back pain.
People who underwent pain reprocessing therapy (PRT), which is an emerging psychological intervention aimed at retraining the brain to interpret pain in a less threatening way, saw notable improvements in chronic back pain intensity as well as modest improvements in sound unpleasantness.
The link between chronic pain and hypersensitivity
Sound is primarily processed in the auditory cortex of the temporal lobes of the brain, which are located near your ears. And deeper regions in that area, such as the insula, help shape the emotional experience of sensations, including pain and certain sounds.
In the study, the researchers analyzed brain scans of 142 adults with chronic back pain and compared them to 51 people without pain. Using functional MRI scans to monitor blood flow and other indicators, the researchers asked people to listen to low- and high-intensity noxious sounds and rate the unpleasantness, such as the knife screeching as it scrapes across glass.
The researchers found not only did those in pain rate the sounds as more unpleasant, their brain scans showed a stronger reaction than those who were pain-free.
“It confirmed what they were telling us, that the sounds really were more unpleasant,” he said.
Katherine Martucci, an associate professor of anesthesiology at Duke University School of Medicine who studies chronic pain but was not involved in the study, said the findings could help people who may not connect their chronic back pain to sound, vision or pressure hypersensitivities, which are more commonly associated with migraines or conditions such as fibromyalgia.
It’s not clear if people develop heightened sensitivity as a consequence of their back pain, or if people with preexisting hypersensitivity are more vulnerable to developing chronic pain, said Sean Mackey, chief of the division of pain medicine at Stanford University.
In either case, the findings of the study “provide an additional piece to the puzzle that chronic pain is associated with more generalized multi-sensory amplification,” he said.
The role of pain therapy
The participants with chronic back pain entered a clinical trial for PRT, which uses psychological techniques, including education and guided meditations that focus on bodily sensations, to help retrain the brain to perceive those pain sensations as non-threatening rather than dangerous. After treatment, they had a modest reduction in the unpleasantness of low-intensity sounds, but not high-intensity (or louder) ones. The nervous system can sometimes interpret low-intensity, non-noxious sounds as threatening, and PRT may help, said Matt Schumann, a psychologist at Mayo Clinic who uses PRT to treat people with chronic pain.
“It’s not uncommon for the patients that I work with to not only experience difficulties with chronic pain, but also sensitivities to lights, sounds and other sensations,” he said.
Schumann noted that although the study findings were promising and showed some improvements in auditory sensitivity after PRT, the evidence was “not very robust and requires additional study,” so it’s not clear whether PRT would help everyone with sound sensitivity.
In the future, Ashar said he wants to see research exploring other senses, such as sight, smell and taste, to determine whether there is “a broad, multi-sensory amplification phenomenon with chronic pain.”
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