The International Association for the Study of Pain (IASP) defines pain as "an unpleasant feeling and emotional experience in response to, or described in, actual or potential tissue damage." It is possible to distinguish three main types of pain according to their evolutionary profile: acute pain, procedural pain and chronic pain.
It is linked to tissue damage whatever its origin (mechanical, inflammatory, etc.)
It is linked to care (blood test, care, mobilization, etc.).
It is defined as a multidimensional syndrome expressed by the person who has it.
There is chronic pain, regardless of its topography and intensity, when the pain has more than one of the following characteristics:
- persistence or recurrence, which lasts beyond what is usual for the presumed initial cause, especially if the pain has been progressing for more than 3 months; insufficient response to treatment; - significant and progressive deterioration due to pain, the patient's functional and relational capacities in his daily activities of life, at home, at school or at work.
When it becomes chronic, pain loses its wake-up call and becomes a disease in itself regardless of its origin. Chronic pain is frequently associated with reinforcing factors that participate in its maintenance such as:
- psychopathological manifestations;
- an insistent request by the patient to resort to drugs or often invasive medical procedures, whereas he declares their ineffectiveness to relieve;
- difficulty for the patient to adapt to the situation.
Chronic pain must be understood according to a bio-psycho-social model, its management based first on an evaluative approach and then on treatment, often multi-modal, the objective of which is rehabilitative.
It is possible to distinguish three types of chronic pain according to the mechanisms at the origin of the latter:
- Pain caused by excess nociception is linked to the persistent and excessive stimulation of peripheral pain receptors: the nociceptors.
- Neuropathic pain is linked to an injury or disease affecting the somatosensory system (nervous system)
- Dysfunctional pain is linked to impaired pain control systems with no lesion identified.
Impact Prevalence Two recent studies estimate the prevalence of chronic pain at 20% of the French population (Bouhassira et al, 2008, Brefel-Courbon et al, in press). The causes of chronic pain can be diverse, with rheumatological pain in mind (low back pain, fibromyalgia, myofascial syndromes, osteoarthritis, which affect 35-40% of the population concerned), followed by headaches (20% in specialized structures), neuropathic pain (multiple sclerosis, shingles or post-traumatic pain, post-surgical) and pain induced by cancer or its treatment. Cost Few studies are available on the subject. An Australian study estimated, in 2008, a cost of chronic pain at 24 billion euros the annual cost of chronic pain. Australia's population was 21,450,000 in 2008. If we relate this study to the French population, with a similar distribution, which counted on January 1, 2017, 66,991,000 individuals, we arrive at an overall cost of 75 billion euros per year. This calculation is not precise but it gives an idea of the public health problem posed by chronic pain.