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Understanding Pain

The fundamentals of pain

Pain is defined as an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.1 Pain has many dimensions and can vary in intensity, location in the body and duration of time. Depending on the type of pain, it can feel like throbbing, burning, shooting or tingling and can range in intensity from mild to severe.3,4 In addition to the physical impact, it can also have psychological, emotional and social effects on everyday life.3

Sometimes the cause of pain is obvious, such as from injury, and other times the source might come from an underlying condition. In some cases, it can be difficult to categorise the exact cause of pain.3

What happens in the body when we encounter a harmful stimulus?

Pain is a normal response to actual or potential injury to the body but can also occur without a clear cause:3,5,6

The three different mechanisms that can lead to the perception of pain: Harmful stimuli, Signal, Pain is felt

There are three different mechanisms that can lead to the perception of pain. In some cases, more than one mechanism may be involved.

Sports injury

1. Nociceptive pain

This type of pain is typically caused by damage to the body’s tissues from either injury or inflammation. Examples include:5,7,8

  • Sports injury
  • Arthritis
  • Appendicitis

2. Neuropathic pain

This type of pain is typically caused by damage to nerves. This damage can be due to lesions in the nervous system, diseases that affect the nerves or injury. Examples include:3,5,9

  • Peripheral neuropathic pain e.g., painful diabetic peripheral neuropathy, chemotherapy-induced neuropathy
  • Post-stroke pain
  • Spinal cord injury
  • Cancer-induced neuropathic pain
Cancer pain
Non-specific back pain

3. Nociplastic pain

This type of pain occurs without clear evidence of actual or threatened tissue damage or lesions and diseases of the nervous system. Examples include:10

  • Fibromyalgia
  • Complex regional pain syndrome
  • Non-specific back pain

What is the difference between acute and chronic pain?

Pain is complex and is not only classified by the mechanisms above, but also by severity, location in the body and duration.2 One of the most common ways to classify pain is by the duration of time someone has been experiencing pain:

Acute Pain Chronic Pain
Lasts for less than 3 months11 Lasts for longer than 3 months12
Occurs usually in response to tissue trauma and related inflammatory processes13 Can be due to an underlying disease such as cancer or arthritis3
OR
Has no obvious cause5 or may continue after the original injury has healed3
Serves a useful and life sustaining (protective) function14 Typically serves no adaptive purpose5
Poorly controlled acute pain can be a factor leading towards chronic pain15 Influenced by a number of interconnected factors, including:13
Biological: genetics, age, sex, sleep, hormones and internal pain regulation systems
Psychological: poor sleep, anxiety or depression
Sociocultural: low educational attainment, culture and poor social support

Chronic Pain

In 2019 the IASP and the World Health Organization recognized chronic pain as a health condition in its own right.13 Some of the most common types of chronic pain are:16

Chronic Pain Conditions

Who is affected by chronic pain?

Chronic pain is an enormous global health problem17 and affects around 1 in 5 adults worldwide.18,19,20

What are some factors that can increase the likelihood of experiencing chronic pain?

Icon ageing
Chronic pain becomes more common with increasing age.21
Icon female employee
Women are more likely to report or experience chronic pain than men22 and report a higher level of pain intensity and higher pain-related disability than men.23
Icon social
Chronic pain is associated with low educational attainment, culture and poor social support.13

Pain is a dynamic consequence of a host of biological, psychological, and social factors; hence, guidelines have recommended interdisciplinary treatment, which ideally makes use of a personalised approach with a shared decision-making.13

The serious impact of chronic pain

Chronic pain exerts an enormous personal and economic burden, and it is considered to be one of the main causes of disability:13,19

%

Up to 90% of adults with chronic pain experience clinically significant insomnia²⁴

%

of patients with chronic pain are less able or unable to do household chores²⁵

%

of chronic pain patients have difficulty maintaining an independent lifestyle²⁵

%

of patients with chronic pain have relationship difficulties²⁵

Mental Wellbeing:

Chronic pain can have a significant impact on mental health and wellbeing.13 Research has shown that more than 50% of patients with chronic low back pain have depression and anxiety,26 and people suffering from chronic musculoskeletal pain with both depression and anxiety are likely to experience more severe pain and pain-related disability.27

The Economy:

The cost of chronic pain is significant:13,19,28,29

US

US

Chronic pain affects 1 in 3 Americans, costing up to $635 billion per year²⁸

Europe

Europe

Across Europe, the cost of chronic pain is estimated to be as high as €300 billion

Chronic pain also increases the risk of other health problems and social exclusion.30

Employment:

Chronic pain affects people’s ability to do their jobs effectively.

  • In the US, people with chronic pain worked 7.5 days less than those without chronic pain.31
  • In the EU, more than 50% of people are prevented from doing their work because of chronic pain.32
  • In the EU, chronic pain has substantial negative impacts on productivity at work.32

Having chronic pain may also affect employment. A survey revealed that less than 20% of people with chronic pain receive occupational rehabilitation in order to remain at work.32 Additionally, research in the UK found that chronic pain was present in 79% of those who were unable to work because of ill health and only in 40% of those in paid employment.33

References
  1. Raja SN, et al. Pain. 2020;161(9):1976-1982.
  2. Stanos S, et al. Postgrad Med. 2016;128(5):502-515.
  3. Orr PM, et al. Crit Care Nurs Clin N Am. 2017;29:407–418.
  4. Fink R. Bayl Univ Med Proc. 2000;13(3):236–239.
  5. National Pharmaceutical Council. Pain: Current Understanding of Assessment, Management, and Treatments. 2001. Available at: https://www.npcnow.org/sites/default/files/media/Pain-Current-Understanding-of-Assessment-Management-and-Treatments.pdf. Accessed May 2022.
  6. Yam MF, et al. Int J Mol Sci. 2018;19(8):2164.
  7. Igolnikov I, et al. Chapter 39, Handbook of Clinical Neurology. 2018:423–430.
  8. Prescott SA and Ratte S. Chapter 23, Conn's Translational Neuroscience. 2017:517–539.
  9. Nicholson B. Am J Manag Care. 2006;12(Suppl 9):S256–62.
  10. Trouvin AP and Perrot S. Best Pract Res Clin Rheumatol. 2019;33(3):101415.
  11. World Health Organization (WHO). International Classification of Diseases 11th Revision (ICD-11). MG31 Acute pain. 2019. Available at: https://icd.who.int/browse11/l-m/en#/http%3a%2f%2fid.who.int%2ficd%2fentity%2f1404135736. Accessed May 2022.
  12. World Health Organization (WHO). International Classification of Diseases 11th Revision (ICD-11). MG30 Chronic pain. 2019. Available at: https://icd.who.int/browse11/l-m/en#/http://id.who.int/icd/entity/1581976053. Accessed May 2022.
  13. Cohen SP, et al. Lancet. 2021;397:2082–2097.
  14. European Pain Federation. What is the definition of pain? 2013. Available at: https://europeanpainfederation.eu/wp-content/uploads/2016/06/CoreCurriculumPainManagementEFIC_Version130718.pdf. Accessed May 2022.
  15. European Pain Federation. The Pain Management Core Curriculum for European Medical Schools. 2013. Available at: https://europeanpainfederation.eu/wp-content/uploads/2016/06/CoreCurriculumPainManagementEFIC_Version130718.pdf. Accessed May 2022.
  16. Treede RD, et al. Pain. 2019;160(1):19–27.
  17. Goldberg DS and McGee SJ. BMC Public Health. 2011;11:770.
  18. Varrassi G, et al. Curr Med Res Opin. 2010;26(5):1231–1245.
  19. Pain Alliance Europe. Survey on Chronic Pain. 2017: Diagnosis, Treatment and Impact of Pain. 2017. Available at: https://www.pae-eu.eu/wp-content/uploads/2017/12/PAE-Survey-on-Chronic-Pain-June-2017.pdf. Accessed May 2022.
  20. Treede RD, et al. Pain. 2015;156(6):1003–1007.
  21. Breivik H, et al. BMC Public Health. 2013;13:1229.
  22. Bartley EJ and Fillingim RB. Br J Anaesth. 2013;111(1):52–58.
  23. Stubbs D, et al. Pain Medicine. 2010;11(2):232–239.
  24. Nijs J, et al. PMR. 2020;12(4):410–419.
  25. Breivik H, et al. Eur J Pain. 2006;10(4):287–333.
  26. Oliveira DS, et al. Pain Medicine. 2019;20(4):736–746.
  27. Bair MJ, et al. Psychosom Med. 2008;70(8):890–897.
  28. U.S. Department of Health and Human Services. Pain Management Best Practices Inter-Agency Task Force Report: Updates, Gaps, Inconsistencies, and Recommendations. 2019. Available at: https://www.hhs.gov/sites/default/files/pmtf-final-report-2019-05-23.pdf. Accessed May 2022.
  29. Gaskin DJ and Richard P. J Pain. 2012;13(8):715–724.
  30. Phillips C, et al. Health Policy. 2008;88:166–175.
  31. Yong RJ, et al. Pain. 2022;163(2):e328–e332.
  32. Pain Alliance Europe. Survey on Chronic Pain and your Work Life. A survey in 14 EU countries. 2018. Available at: PAE-Survey-2018-Pain-And-Your-Work-Life.pdf (pae-eu.eu). Accessed May 2022.
  33. Macfarlane G, et al. Br J Pain. 2015;9:203–212.