Pain is considered chronic when it lasts for weeks, months, and even years. Etiologies include trauma and conditions such as arthritis, cancer, infection, degenerative disc disease, and neuropathies. Common complaints are headaches, low back pain, arthritis, and neurogenic pain (pain that results from damaged central nervous system or peripheral nerves).
According to the American Academy of Pain Medicine, more than 1.5 billion people worldwide suffer from chronic pain, and approximately 3-4.5% of the global population suffers from neuropathic pain, with incidence rate increasing complementary to age. In 2011, the Institute of Medicine of the National Academies stated that 116 million Americans suffer from chronic pain. The next closest condition is diabetes – at 25.8 million Americans (this is the total of diagnosed with an estimate of undiagnosed).
The total annual cost of health care due to pain ranges from $560 billion to $635 billion (in 2010) in the United States. More than half of all hospitalized patients experience pain in the last days of their lives. Although therapies exist to alleviate most pain for those dying of cancer, research shows that 50-75% of patients die in moderate to severe pain. An estimated 20% of American adults (42 million people) report that pain or physical discomfort disrupts their sleep a few nights a week or more.
In 2006, a National Institute of Health Statistics survey indicated that low back pain was the most common chronic pain (27%). This was followed by severe headache or migraine pain (15%), neck pain (15%) and facial ache or pain (4%). Back pain is the leading cause of disability in Americans under 45 years old. More than 26 million Americans between the ages of 20-64 experience frequent back pain.
How does chronic pain impact quality of life? The NIHS survey revealed that almost two-thirds (59%) of respondents reported deleterious impact on their overall enjoyment of life. More than three-quarters (77%) reported feeling depressed; 70% said they have trouble concentrating; 74% said their energy level is impacted by their pain; and 86% reported an inability to sleep well.
Chronic pain is very complex and a difficult health concern to treat. One reason is that the longer it goes on, the more systems become affected. Then there’s the phenomenon of pain sensitization syndrome. This is where sensitization of receptors is related to inflammatory and other non-inflammatory mediators at the nerve ending. Basically, the nerve fires at a lower threshold than before and even mild or relatively noxious stimuli activate the receptors, causing more pain. This can happen to the point where pain can be constant even without a triggering event. It can also increase in intensity and in other regions of the body.