Vitamin D Deficiency Linked To Chronic Pain

Paul McCabe et al from the University of Manchester analysed data from the European Male Ageing Study and found that men with vitamin D deficiency at the start of the study were more than twice as likely to experience ongoing widespread pain over the next 4 years as those with high levels of vitamin D. It was noted that the men with chronic widespread pain were more likely to be physically active, obese, depressed and to have other health problems. Once these other factors were taken into account the link between vitamin D and pain disappeared.

However, John McBeth et al analysed data from the same study and found that even after adjusting for other health factors, pain remained moderately associated with increased odds of having low vitamin D levels. This is supported by a 5-year longitudinal study published last year by Laura Laslett et al in which vitamin D deficiency was found to predict incidence or worsening of knee pain and hip pain.

There seems to be a link between a deficiency of vitamin D and pain but could supplementation with vitamin D help to decrease pain? Between 2008 and 2010, Shreuder et al conducted a study in Holland and they did indeed find a small positive benefit (less pain and better function) after taking a high dose of vitamin D for 6 weeks.

What could the mechanism behind vitamin D and pain be? Tague et al found that vitamin D deficiency in rats can lead to a hyperinnervation of skeletal muscle which is likely to contribute to muscle hypersensitivity and pain.

Vitamin D is naturally present in a few dietary sources such as fish oils, mushrooms, eggs and liver. Other than supplements, sunlight exposure is the best source of vitamin D for most of people.

Potential Advances In The Treatment Of Osteoarthritic Pain

In a recent study published in Annals of the Rheumatic Diseases and reported in Medical News Today, Sara Kelly and colleagues from the Arthritis Research UK Pain Centre at The University of Nottingham have discovered a new way to possibly decrease the chronic pain affecting people with osteoarthritis. They studied a protein receptor called TRPV1 which is present in the synovial membranes of joints. These receptors are responsive to pain. Injecting TRPV1 agonists directly into the joint produced pain relieving effects.

The study was performed on rats so before being used on humans the results will need to be replicated in clinical trials and monitored for potential side effects.

Until then the best self-help advice for those with osteoarthritis is weight loss (if it affects joints in the lower limbs), stretching & strengthening exercises and maintaining moderate levels of activity. Nutritional supplements can also help (see related articles here).

Poor Sleep Linked To Pain

A new study by Arthritis Research UK Primary Care Centre at Keele University and published in Arthritis & Rheumatology has identified factors associated with an increased risk of developing widespread pain in adults over 50. Of the factors measured, non-restorative sleep was the strongest independent predictor of new onset widespread pain.

Stress Management Could Help Decrease Pain

A recent study by Dr. Pierre Rainville and Étienne Vachon-Presseau from the University of Montreal has shed some light on the relationships between stress, the brain and pain. Their study compared 16 patients with chronic back pain with a control group of 18 healthy subjects. They found that back pain patients had higher levels of cortisol than subjects from the control group. Cortisol is produced by the adrenal glands and is secreted in response to stress. It’s a steroid hormone that increases blood sugar levels, suppresses the immune system, and may decrease bone formation; so an excess, particularly when maintained over a long period, is detrimental to health. The higher cortisol levels were associated with smaller hippocampal volumes. The hippocampus is a part of the brain that is involved in learning, memory and regulation of emotion. People with depression and post-traumatic stress disorder have been found to have hippocampal atrophy. The subjects with chronic back pain had stronger responses to pain stimuli in a brain region involved in anticipatory anxiety in relation to pain. Brain activity in response to the painful stimulus partly reflected the intensity of the patient’s current clinical pain condition.

The findings can be summarised in the following flow chart.

The authors suggest that stress management techniques such as relaxation and meditation should be used to complement medical treatments in patients with pain. They believe this can help to decrease the impact of pain and perhaps even prevent chronicity.

Chronic Pain Alters DNA

The team of researchers led by Prof. Laura Stone at McGill University recently found that 6 months after inflicting nerve injuries on mice, the mice still displayed signs of skin hypersensitivity and motor impairment. This was associated with epigenetic changes in the amygdala and prefrontal cortex of the brain. Epigenetics explains how genes can be switched on and off. It’s the study of mechanisms by which the environment controls gene activity. Interestingly, the DNA changes were reversed by placing the mice in a more stimulating environment (three mice per cage, a running wheel mounted on a plastic hut and marbles). Whereas, placing the mice in an impoverished environment (one mouse per cage in the absence of a running wheel, marbles or any other forms of enrichment) didn’t restore normal DNA. DNA changes were found to correlate to hypersensitivity. In other words, placing the mice in a stimulating environment helped decrease their pain.

Long-term Use Of Opioids Lowers Testosterone Levels

A recent study by Rubinstein et al. published in The Clinical Journal of Pain has shown that long-term use of opioid painkillers by men is associated with lower levels of testosterone. This effect is much more prevalent when using long-acting opioids. Low testosterone or hypogonadism, as it’s also known, has been linked with decreases in muscle mass, bone density, cognition, mood, sex drive and general quality of life.

Pain And Emotion

Although mainly about the effects of emotion on reason, ‘Descartes’ Error‘ by Antonio Damasio contains a few fascinating nuggets on pain. He distinguishes 2 components to pain:

• Sensory perception from skin, mucosa, muscle, organ, etc. – the nerve endings stimulated in an area of the body lead to a ‘pain image’, a temporary representation  of body change in the brain. This is no different from any other kind of body perception and if it were all, we would not be inconvenienced.
• Emotion and feeling – it’s from these body-state changes that the unpleasant feeling of suffering is formed. “Suffering puts us on notice and offers us the best protection for survival, since it increases the probability that individuals will heed pain signals and act to avert their source or correct their consequences.“

Damasio’s views on emotion/feeling and pain are probably the result of his experience with the eminent Portuguese neurosurgeon Almeida Lima. Lima worked closely with Portuguese neurologist Egas Moniz. Together they developed prefrontal leucotomies, later known as lobotomies, during the 1930s. In 1949 Moniz received the Nobel Prize in medicine for his work. Damasio recalls following Lima on a pre-operative visit of a patient with trigeminal neuralgia, a condition that causes severe facial pain. “He was crouched in profound suffering, almost immobile, afraid of triggering further pain. Two days after the operation, when Lima and I visited on rounds, he was a different person. He looked relaxed, like anyone else, and was happily absorbed in a game of cards with a companion in his hospital room. Lima asked him about the pain. The man looked up and said cheerfully “Oh, the pains are the same, but I feel fine now, thank you.” Clearly, what the operation seemed to have done, then, was abolish the emotional reaction that is part of what we call pain. It had ended the man’s suffering.”

Obviously, lobotomies are extreme measures and they can cause serious side effects. This is certainly the reason fewer and fewer operations are being performed. Nowadays these operations are called psychosurgery and they have become much more precise. The important point is Damasio’s view on the link between pain and emotion. It corroborates a lot of the research being done on chronic pain. Hence, the importance of addressing the emotional part. Fortunately, there are now safer more humane ways of doing it, like relaxation, meditation, cognitive behavioural therapy, neuro-linguistic programming and hypnosis.

Mindfulness Changes Pain

I read an interesting passage in ‘Mindfulness’, Ellen Langer’s insightful book on social psychology.

“Patients are often certain that pain is inevitable in a hospital. Caught in such a mindset, they assume that, without the help of medication, pain cannot be controlled. In our experiment, we tried to learn whether people could control their experience of pain by putting it in a different, more optimistic context.

Patients who were about to undergo major surgery were taught to imagine themselves in one of two situations: playing football or preparing for a dinner party. In the midst of a rough skirmish on the football field, bruises are hardly noticed. Similarly, cutting oneself while rushing to prepare dinner for ten people who will be arriving any minute might also be something one would hardly notice. In contrast, a paper cut suffered whilst reading a dull magazine article quickly becomes the focus of attention. Through examples of this sort, participants in the study were taught that, rather than being inevitable, much pain we experience appears to be context-dependent.

Hospital staff, unaware of our hypothesis, monitored the use of medication and the length of stay for the participating patients in the experimental group and in the control groups. Those patients who were taught to reinterpret the hospital experience in nonthreatening ways took fewer pain relievers and sedatives and tended to leave the hospital sooner than the untrained patients. The same hospital experience seen through psychologically different eyes is not the same experience, and the difference could be measured in lower doses of medication and quicker recoveries. This reappraisal technique effectively loosened the hospital mindset and, by showing that pain was not a certainty, gave the participants more control over their convalescence.”

This experiment clearly demonstrates that changing our mindset can change our experience of pain!

Chronic Pain And Emotion

Professor Apkarian has studied chronic pain for over 20 years. In a recent study looking into people with recent back pain, he was able to predict with 85% accuracy those that would go on to develop chronic back pain! How? By noticing an increased level of cross-talk between two specific parts of the brain…suggesting that the more emotionally the brain reacts to the injury…the greater the likelihood of developing chronic pain. The researchers also found that the subjects that developed chronic back pain lost grey matter density…this is in accord with earlier studies that have measured brain atrophy in people with chronic pain. These changes can be compared to those that occur with aging.

BBC Horizon’s Secret World Of Pain

Last year BBC Horizon created a documentary entitled ‘The Secret World of Pain‘. I watched it on YouTube a week ago, thought it was really well put together and so decided to share the most salient points.

Pain is one of our most ancient survival mechanisms and it protects and alerts us to danger. The SCN9A gene is responsible for regulating electrical signals that send pain sensation to the brain. Certain rare genetic disorders can prevent people from feeling pain…these unfortunate people are much more susceptible to burns and other injuries…this underlines just how crucial the sensation of pain is to us.

Pain can alert us to injury or potential injury, but why doesn’t it reflect the extent of injury…and why is it so subjective? There are a couple of possible reasons for this. Key experiences in early life have been found to be as important to pain perception as genetics. Early life is crucial for the formation of pain pathways which are shaped in response to touch. For example, premature babies are exposed to a lot more painful procedures and this alters the normal development of their pain pathways…the overdevelopment of pain pathways makes them hypersensitive and much more likely to experience pain in the future.

Pain and pleasure are both perceptions…psychological constructs…and so environment, context, decision-making, attention, distraction, motivation, emotion, etc can change how signals are processed and hence influence pain. There is a limit to how much information the brain can process at any one time…focussing attention on something pleasant (distraction) decreases the brain’s ability to process pain signals.

Subjects in an experiment were shown a triangle and exposed to a low temperature which they rated as 3/10 on a pain scale…this was repeated several times…they were then shown a square and exposed to a high temperature which they rated as 7/10 on a pain scale…this was repeated several times…they were then shown the square but exposed to the low temperature instead…surprisingly they rated the pain as 5/10. The researchers concluded that anxiety had affected their sensation of pain. I would add that expectation and conditioning may also have played a part.

Chronic pain is pain that persists long after an injury has healed…and therefore serves no purpose. It affects 1 in 5 people and is one of the biggest medical health problems. It can become an enormous burden on the brain and leads to chemical and structural changes. MRI scanning has revealed that people with chronic pain have less grey matter in the pre-frontal cortex. The answer to chronic pain may lie in reversing these changes. Encouragingly, electromagnetic impulses to the brain cortex have helped to normalise changes and to decrease pain, albeit temporarily. Research into this sort of treatment is extremely promising but still in its infancy.