• Wednesday, July 24, 2024
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A world of pain


Pain is ubiquitous in life. Inextricably bound to consciousness, it is an experience that all living creatures with advanced nervous systems share. For our ancestors, whose lives were fraught with danger, pain conferred an evolutionary advantage, signaling the need to separate oneself from its immediate source. But evolution has failed to keep pace with biomedical and technological advances, allowing chronic pain (pain that persists beyond an acute injury or condition) to become a disease in itself.

It is difficult to overestimate chronic pain’s societal impact. According to the US Institute of Medicine, one in three people suffer from chronic pain – more than from heart disease, cancer, and diabetes combined. Pain is the leading cause of disability, especially back pain among people under 45 years of age and joint pain in older individuals. In the United States alone, chronic pain is estimated to cost more than $600 billion annually.

Pain can be classified according to a variety of factors, such as duration or location. But the most useful categorization is based on mechanism. Nociceptive pain, which arises from damage to non-nervous tissue, occurs when, say, a person twists an ankle. An example of chronic nociceptive pain is arthritis. Neuropathic pain, by contrast, arises after a lesion or disease affects the nervous system. Nerve damage resulting from diabetes (diabetic neuropathy) and persistent pain after shingles (postherpetic neuralgia) are among the most common causes.

Chronic pain is difficult to treat; even the most effective medications provide only modest relief to a minority of patients. This can be explained partly by pain’s subjective nature, and partly by the fact that its source can be difficult to pinpoint.

Although neuroscientists are adept at studying pain, animal models fail to account for its “affective-motivational” component – that is, pain’s emotional, cognitive, and contextual features. Indeed, physiological indicators have less of an impact on a patient’s prognosis after a painful injury than psychological and social factors such as depression or poor coping skills. The problem is that subjective measures are much more difficult to study – not least because they are associated with high placebo response rates.

Unrealistic expectations exacerbate these psychological impediments to progress. In an era of instant access, people often expect immediate relief from symptoms, which is difficult to achieve when it comes to chronic pain.

For example, the best way to relieve back and neck pain is often to exercise, while treating underlying contributing factors like obesity. But few people are willing to devote the time and effort that such a therapeutic plan demands; they would prefer an injection, operation, or medication. When there is no instant fix available, they can become discouraged, hampering their recovery further.

Making matters worse, people are being inundated with information – and often misinformation – through television, the Internet, and other direct-marketing channels. This fuels misconceptions and, in many cases, gives people false hope about the kind of relief they can expect from a particular drug or treatment.

Not even physicians are immune to these influences; indeed, in some cases, they actually create the bias. For example, studies of epidural steroid injections for back pain have been shown to be almost three times more likely to yield positive results when conducted by doctors who routinely administer them.

Financial incentives have compounded the problem, leading to some alarming trends. Procedures, operations, and prescription opioid use aimed at curbing chronic pain have increased dramatically over the last decade, driving up health-care costs, while failing to stem the increase in the prevalence of pain or the number of disability claims.

This is particularly problematic in countries where health-care delivery is based on a fee-for-service model. The rate of spine surgery in the United States, for example, is more than twice as high as in Europe. And, despite having less than 5% of the world’s population, the US accounts for more than three-quarters of global opioid consumption – leading to a surge in addiction rates and overdoses.

What can be done to improve management and treatment of chronic pain? For starters, health-care providers and individuals should view chronic pain more as a “syndrome” than a symptom – one that may not be “curable.” For patients who have not responded to conventional treatment, restoring function should replace eradicating pain as the primary objective.

Similarly, patients must recognize that there are no “silver bullets” for pain treatment. Indiscriminate use of procedures that may benefit only a select few patients merely drives up health-care costs. Likewise, for chronic non-cancer pain, there is virtually no evidence to support the long-term use of high doses of opioids, which often do more harm than good. The long-term pain treatment with the strongest empirical support involves lifestyle modifications such as exercise, stress reduction, and weight loss – all of which require significant time and effort.

Finally, researchers should compare the long-term cost-effectiveness of different treatments in typical chronic-pain patients. Such an approach would be more relevant and generalizable than industry-sponsored short-term studies that compare new treatments to placebos in a fastidiously chosen population that does not reflect real-world conditions.

A thorough and realistic understanding of the nature of chronic pain is crucial to devising effective treatments. Indeed, without better evidence, efforts to help patients may well end up creating more problems than they solve.

Steven P. Cohen