Pain is caused by inflammation. A study of nearly 100 patients with low back pain found that early inflammatory responses may protect against chronic pain.
The study, which included mouse models of persistent pain and a population-level analysis of painkiller use, seems to go against mounds of evidence indicating that inflammation drives widespread chronic pain.
Acute inflammation is the first wave of immune cells led by neutrophils, a type of white blood cell.
The study points to the role inflammation plays in chronic pain, which lasts six months or more.
Anti-Inflammatory drugs, a mainstay of pain treatment, may be counter-productive for long-term outcomes for people with low back pain, according to findings. This study only followed White adults for three months, so more diverse studies are needed.
Despite advances in the understanding of social, psychological, and genetic factors, as well as brain processes associated with chronic low back pain, we don't know much about the mechanisms underlying the acute-to-chronic pain transition.
There is a huge need for better pain relief. In terms of years lived with disability, low back pain is the most disabling of all chronic conditions.
To treat it, we need to better understand how chronic pain develops and why acute pain in some patients persists in others.
Acute pain lasts for less than three months. Chronic pain can be a result of a complex interplay between the body's immune and nervous systems.
Parisien and colleagues looked at the expression of genes in the immune cells of 98 patients with acute low back pain, and compared it to the expression levels in the immune cells of patients who had their painbate after three months.
The study found that people with low back pain had inflammatory responses. Dynamic changes in several thousand genes were observed in immune cells, but not in people with persistent pain.
The main reason why they were overlooked was because of the short-lived inflammatory responses. Control subjects who never experienced pain in the first place were not included in the analysis.
In the mouse studies, early treatment with anti- inflammatory drugs prolongs pain even though it is relieved in the short term, whereas no such effect was seen with painkillers that don't act on inflammation, such as lidocaine.
In other experiments, mice that were deficient in neutrophils took longer to resolve pain signals, while mice that were injected with the neutrophils did not develop long- lasting pain.
In this case, the animal studies provide mechanistic insights into pain processes, so it almost goes without saying that mice are only rough models.
The team used data from the UK Biobank to analyze the usage of painkillers among people with low back pain.
They found that people who used NSAIDs such as aspirin had a 1.76-fold higher risk of reporting back pain 2 to 6 years later than people who did not use NSAIDs.
Measures of pain intensity and psychological distress were not captured in the data.
The researchers did account for age, sex, and ethnicity in the analysis, and when they factored in antidepressant use as a proxy for psychological distress, the findings did not change.
The results led Parisien and colleagues to conclude that pain resolution could be impaired in people who have acute inflammatory responses.
The author of the study says that they always think of pain as a pathological process.
It is an active adaptational process that is happening in people who resolve pain, and have chronic pain is the absence of it.
There are many types of chronic pain and painkillers are just one part of the pain management picture.
According to recent research, the key to managing chronic low back pain is psychotherapy, which can help to reduce pain intensity and improve physical function by tackling the mental aspects of pain alongside physical remedies.
Science Translational Medicine published the study.
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