One of the most widely accepted definitions of Pain given by The International Association for the study of pain is ‘’an unpleasant sensory & emotional experience associated with actual or potential tissue damage , or described in terms of such damage’’.
Everything from our genes to our psychological makeup can affect our sensitivity to physical pain. What might be considered one person’s niggle might be another person’s nightmare! A simple blood pressure cuff with increasing pressure may cause tingling pain in those susceptible and might not be discomforting at all for a few.
Thus what can be deciphered as a baseline to this is that “pain threshold “(the level at which we feel a stimulus is painful) & ‘’pain tolerance” ( how much a person can take pain before breaking down ) aren’t always the same.
For example, chronic pain patients can have a lower pain threshold because they process pain very quickly, but a higher pain tolerance as they are used to living with pain and adapted to it. Pain itself is not just a reflection of noxious input but also an expression of plasticity in the brain.
Factors affecting pain perception in individuals includephysical, psychological, emotional, neurological & genetical, cultural, lifestyle induced to name a few. The reason why some people are more sensitive than others comes down to how our body modulates pain — from the skin to the brain — and the structure of the brain itself.
Reasons
It all begins with a bunch of sensory receptors (known as nociceptors) detecting an unpleasant stimuli. These are transformed into pain signals that are then conducted throughout the central nervous system via a series of ‘pain pathways’.
There is a pathway that falls from the periphery (the skin), into cell bodies contained in the ganglion and up the spinal cord. From there, the fibres ascend to the brain. Firstly, individuals each have a different expression of the receptors that respond to a particular stimulus — whether this be thermal (for example, heat) or mechanical.
Secondly, the pain pathways are complicated. In each of these layers through which the information passes, there can be some modulatory effects (even in the cortex in the brain) that either reduce or increase the level of pain experienced. This is where our emotional status comes in. There are connections between various areas in the brain that can modulate this system as well.
Factors associated with chronic pain can be modifiable or non modifiable.
Modifiable Factors
1. Pain: It is perhaps the most important clinical risk factor for chronic pain. The more severe the acute pain, greater the number of pain sites, the more likely it is that chronic pain will develop
2. Mental Health: Anxiety, depression & catastrophising beliefs about pain have been associated with poor prognosis in patients with chronic pain.
3. Multimorbidities: Upto a Third of people with coronary heart disease experience chronic pain & almost a similar percentage of patients with chronic obstructive pulmonary disease experience similar symptoms. Conditions like diabetes, hypertension have shown to reduce pain thresholds.
4. Smoking: Heavy smokers tend to report more pain locations and increased intensity compared with those who have never smoked. Although some have postulated that the direct aversive physiological effects of smoking cause or aggravate painful conditions , concurrent depressive symptoms may also mediate the effect of smoking on chronic pain outcomes.
5. Obesity: The relationship is much more complex than simply mechanical overload where familial (environmental & genetic) are significant contributors to the association. It is the impact of pain on functional status and health related quality of life that is greater in the obese than in those with normal BMI
6. Nutrition: findings from a recent research suggest that dietary omega-3/omega-6 ratio may have significance for inflammatory pain. Increasing omega-3 intake (found in fish) reduces patient-reported joint pain intensity, morning stiffness and the number of painful joints in patients with rheumatoid arthritis or joint pain secondary to inflammatory bowel disease.
Knowing that the central nervous system has specific nutritional requirements, clinical studies suggest that reducing polyamine-containing foodstuffs (e.g. bran, nuts, soyabean) may reduce hyperalgesia and has shown some early promise in cancer patients with metastatic disease.
Other dietary constituents that show early promise include some flavonoid compounds, alpha-lipoic acid (found in broccoli, spinach, yeast) and vitamin E for diabetic neuropathy.
On the other hand, there is some preliminary evidence to show that medically supervised modified fasting (300 kCal/day) for a defined and limited period (7–21 days) could be useful as an adjunctive therapeutic approach to enhance mood in chronic pain patients who are often affected by depression and anxiety.
Non-modifiable factors
1. Old age : There is generally a higher prevalence of chronic pain in old age,and the occurrence of more severe disabling chronic pain increases with age.
2. Female sex: Chronic pain syndromes generally have a higher prevalence in women. They are found to have lower pain thresholds and lower pain tolerance, experience greater unpleasantness (or intensity) with pain and have different analgesic sensitivity.
3. Influence of ethnicity and cultural background: Pain is a complex personal experience influenced by multiple interactive biopsychosocial processes. However, there exists a similarity in the prevalence of chronic pain between developed (37%) and developing countries (41%) according to WHO World Mental Health Surveys.
4. Genetics: It is clear that there is no unique ‘pain’ gene, but that a complex combination of genetic factors interacts with the psychosocial and lifestyle factors to produce chronic pain. Genes may act at a number of levels to influence the expression of chronic pain, including biological processes and behavioral and emotional responses. Identifying specific genes and their roles, and distinguishing these from other sources of variation (gender, ethnicity, socio-cultural, psychological, etc.) is currently an important challenge.
Take home messages
- The existence of both individual-level and population-level risk factors for the onset or persistence of pain suggests that opportunities for intervention exist at more than one level.
- Chronic pain management dominated by analgesic medication will fail to address adequately the role of activity, psychological factors and social factors in maintaining daily function.
- Clear opportunities exist for all health professionals to facilitate changes in lifestyle that have the potential to improve morbidity and function in patients with chronic pain, simultaneously reducing the risks and impact of common co-morbidities.
- Further research is required to identify the most effective approaches, and this should be a priority for all health services.
This article has been written by Dr. Aishwarya Aiyar who is a Physiotherapist from Seth GS Medical College.
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