According to the International Association for the Study of Pain (IASP), pain is “an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.

Pain is a common experience that nearly every person will confront in their lifetime. For some, it will be brief and the pain will subside within seconds or minutes. Other times, the pain may last a bit longer before resolving on its own. 

Yet, research tells us that for 20% of the population the pain does not go away. In fact, 28% to 61% of people develop chronic pain after they experience acute pain from an injury or surgery. Why? What is the reason?

Each November, U.S. Pain Foundation hosts KNOWvember, an educational campaign, to provide specific, helpful information on a different pain-related topic. This year, the organization aims to better understand and #KnowPain by exploring acute-to-chronic pain—what is acute pain versus chronic pain, what therapeutics exist for both subsections, why acute pain transitions to chronic for some individuals, why increased research and pain education are important, and more. 

As we kick off the month, let’s look at the differences between acute and chronic pain—and why society needs to seek better solutions to manage pain.

Knowing the difference

Pain is the number one reason a person sees a doctor. It also costs the nation up to $635 billion each year in medical treatments, disability payments, and lost productivity. Not all pain is equal when it comes to treatments or progression. We first need to understand definitions:

• Acute pain, defined by the IASP, “happens suddenly, starts out sharp or intense, and serves as a warning sign of disease or threat to the body.” Causes include injury, surgery, illness, trauma, burn, or the process around surgeries/procedures. Acute pain generally lasts from a few minutes to less than six months. It usually disappears whenever the underlying cause is treated or healed.

• Chronic pain, defined by the IASP, is “pain that persists or recurs for longer than three months.” Oftentimes, chronic pain becomes the sole or predominant clinical problem for individuals, and may warrant specific diagnostic evaluation, therapy, and rehabilitation. Neuroscience research has demonstrated that chronic pain can become a disease in itself, with measurable changes in the brain, spinal cord, and peripheral nervous system.

• Acute-to-chronic pain refers to the transition of acute pain to chronic pain. In many cases, when acute pain persists longer than three months, it turns chronic which can last for years or a lifetime. 

Yet despite our best efforts at defining the various types of pain, we still are left with questions regarding that intersection of acute-to-chronic pain—why acute pain transitions to chronic pain for some people and not others, and why there are subpar options to treat and manage it.

The crossroads of pain

There has been much speculation about potential determinants that may increase the likelihood of progression of acute pain to chronic pain. Possible factors include genetics, demographics, past trauma, past health history, the nature of the injury or surgery (for instance, mastectomies carry risk of development of nerve pain), and others. 

Still, there is no solid evidence to show this causation… yet. All that we know is that there is a pain crisis that can no longer be ignored. 

National health agencies are taking an interest. For instance, the National Institute on Aging is looking at advancing pain science. The National Institute of Health’s HEAL (Helping to End Addiction Long-term) Initiative, is a multi-year, multi-agency effort funding major investments into the science of pain.

One of the National Institutes of Health (NIH) programs is focused on investigating the biological characteristics underlying the transition from acute to chronic pain. The Acute to Chronic Pain Signatures (A2CPS) is currently undertaking two longitudinal studies with patients who experience acute pain resulting from a surgical procedure. The goal: “develop a set of objective biomarkers that provide ‘signatures’ to predict if chronic pain is likely to develop or be resolved after acute pain, like an injury or after a surgery.”

The Early Phase Pain Investigation Clinical Network (EPPIC-Net) is another NIH HEALInitiative looking at accelerating early-phase clinical trials of non-addictive treatments for acute and chronic pain. The U.S. Food and Drug Administration (FDA) as well as the Centers for Medicare & Medicaid Services (CMS) are also engaging in the topics of acute and chronic pain. Earlier this year, the FDA released draft  guidance on the development of non-opioid analgesics for acute pain, and CMS recently announced their intention to improve chronic pain care by paying physicians separately to care for Americans who are over 65 or disabled.

These initiatives are a promising step as we continue to navigate the murky landscape of effectively treating both acute and chronic pain, and reducing the likelihood that acute pain will transition to chronic.

Treatment options

As humans, our first inclination when experiencing pain is how to make it stop. We question the best approach to manage acute versus chronic pain: is it rest? When is it better to use heat versus cold? Are OTC’s appropriate or other prescription medications? When will the pain subside?

While there is commonality between pain management options for acute and chronic pain, there are also differences. Typically, treating acute pain focuses on the underlying cause and working toward interrupting the nociceptive, or sensory pain receptor, signals. Chronic pain, is best treated with a multidisciplinary approach that involves more than one therapeutic modality.

The most important thing is making sure your pain is being addressed and managed appropriately, while finding resources and support to help.

Looking forward this November

As we look at the intersection between acute and chronic pain, we hope to:

• Increase awareness of chronic pain as a disease.
• Spur greater research into the causes of chronic pain.
• Provide education about the different treatment options for acute and chronic pain.
• Address the need for collecting population health data about different pain conditions, patient characteristics, like gender, ethnicity, and geographic location, treatment modalities and their effectiveness for different types of pain, costs and more. 
• Highlight the lived experiences of individuals who live with acute and chronic pain 

It’s time to really get to know pain. 

This campaign was created through support from Vertex Pharmaceuticals and Johnson & Johsnon. U.S. Pain Foundation developed the content without review from sponsors. This information is educational only and should not be used as a substitute for advice from a health care professional.