Epidemiology and Risk Factors

Studies regarding the epidemiology of low back pain are highly variable. This is not surprising—it is a condition that is highly specific to each individual patient. Survey studies are difficult because one patient’s perception of pain may be quite different than that of another. The incidence of developing a new episode of back pain has been estimated as low as 4% and as high as 93%.^6–9 On the basis of larger longitudinal studies, this incidence has been estimated to be much lower, between 3% and 5% for episodes where patients sought medical attention. The incidence of back pain that did not require professional medical care was much higher, at 30%.⁷ Prevalence is difficult to study due to variance among study populations and the different factors that may affect the development of low back pain. Studies estimate that 15% to 20% of adults experience memorable low back pain within 1 year and up to 80% experience such pain over a lifetime.^10–13

In terms of age, back problems do not necessarily occur more frequently during the third to fifth decades. When they do, however, they are certainly more often related to claimed disability during this period. These are the prime working years, where low back pain leads to the greatest disability and days off work. Interestingly, the symptoms of low back pain do not become worse with age-related degeneration of intervertebral discs.^1,14–17 Back pain in the elderly is thought to be one of the most important factors to affect the individual state of health.¹⁸ Similar to younger adults, the prevalence of back pain in patients older than 65 years of age is 13% to 49%,¹⁹ but this pain seems to be more episodic and intermittent with a lesser occurrence of chronic pain.²⁰ Despite the relatively high prevalence of abnormal curvature of the spine in adolescents, the chance of these children presenting with low back pain is quite low. Some studies suggest that the peak age for development of back pain in children is 13 to 14 years and that beyond this age, the risk factors for developing back pain in adults also apply in children.^21–23

Risk factors for the development of low back pain are demographic, physical, socioeconomic, psychological, and occupational factors. Many studies of these risk factors are small and include only self-reports of the variables. A review by Hildebrandt discusses 55 personal factors and 24 occupational factors that have been linked to low back pain.²⁴ Many studies have looked at the relationship between socioeconomic status and level of education and the development of back pain. The association seems to be not so much with the incidence of pain but with the ability to adjust to pain. The incidence of disability from back pain appears to be 22 to 25 times higher in patients with less than 7 years of education compared with those with college degrees.²⁵

Observations Regarding Low Back Pain and Disability

First, it is important to differentiate between pain and disability. Both are related in that they are generally subjectively relayed by the patient and are not viewed the same in any two patients. There is no objective measure for either of these disorders. Disability is related to the patient’s perceptions and attitudes about pain^26,27 and may be based on avoidance based on previous painful experiences.^1,28,29 Many people live with low back pain, and few patients view this condition as a disability.

It is also useful to discuss the difference between acute and chronic pain. Acute pain often bears a close relationship to an inciting event and may be thought to stem directly from tissue injury. Chronic pain, on the other hand, is often a behavioral adaptation of an individual who may or may not have had an initial injury. This bears very little relationship to physical injury and is very difficult to treat by medical and surgical means. The failed back syndrome is indeed closely related to this concept. Chronic pain becomes a syndrome of emotional distress, depression, and disease conviction.¹ If these patients are taken to surgery under the misconception that their pain is actually related to tissue injury, they are virtually never cured and are often made worse. Surgery in these patients also plays into the “sick role” and gives them further reason to take time off work and to claim that they are disabled. These patients often clog pain clinics and spine clinics and place a heavy burden on the health-care system.

Despite low back pain and sciatica taking center stage in many medical circles today, there is no evidence that the biology of the problem has changed at all over the years. Back pain is the same as it always has been. It is low back disability that is a new concept. Ninety percent of patients with low back pain become better within 6 weeks in spite of technologically advanced medical and surgical care, or interestingly, no care at all.^1,15,30,31 This is likely a product of the explosion in the size and complexity of the health-care systems of Western countries and individuals’ perceptions that the abilities of modern health care should be able to end pain. Physicians bear some responsibility in this regard because it is they who certify patients with pain to be excused from work, thereby feeding into the concept of low back disability.

Perhaps the most referenced expert to publish on low back pain and disability is Gordon Waddell. In his book The Back Pain Revolution,³² he discusses his time spent in Oman. At the time of his writing, Oman was an emerging, primarily developing country. In the mid-1980s, new oil money soon brought modern medical treatments to this country. At the time, patients with back pain flooded into the newly established clinics seeking treatment for their pain. These patients had very similar problems with similar etiology to patients in developed Western countries. The interesting part is that nearly none of them were off work or “disabled” as a result of their pain. Waddell’s observation was that the patients who were able to escape the confines of their country to have “modern” medical procedures in other countries became disabled after surgery at a much higher rate than those who did not have access to modern medical care. This is another illustration that suggests that low back pain is nothing new but that low back disability is largely a product of modern Western medicine.

Breakdown of the Disease Model of Illness

As mentioned earlier, modern medicine now largely depends on the disease model of illness. This model, which has been adapted over the years from roots in the 16th and 17th centuries, follows a progression from physical signs and symptoms, to diagnosis, to treatment, to cure. This depends directly on the fact the “disease” (pain, in this case) comes from physical pathology and excludes factors such as psychogenic and social issues. As this model breaks down, one can easily see that a prospective therapy does not lead to cure unless there is a true link between a presumed tissue injury and the physical signs of pain. This is probably not the case in the vast majority of patients with low back disability.

Chronic low back pain probably is better considered in the context of a different disease model, the biopsychosocial model. This model stresses the integration of the mind-body continuum, which has been proposed by philosophers since before science was born. This suggests that it is not only the responsibility of the physician to treat the body but also to assist the patient in adjusting to their illness and coping with it mentally. The gate theory of pain and experience with psychosurgery both support the assertion that pain perception requires both sensory and emotional components and can be modified by mental, emotional, or sensory mechanisms.³³

These concepts are very solidly related to the diagnosis and treatment of low back pain. As it turns out, many patients are not satisfied with an office visit without the establishment of a diagnosis based on real pathology. Disc disease has become so popular and common, and patients may be given the nominal diagnosis of disc prolapse without any signs of nerve root compression or radiographic evidence. It is not long until this nominal diagnosis is confused with real disease pathology, and the patient receives the label of discogenic low back pain. These patients may eventually end up being treated with surgery and then bouncing from clinic to clinic when this operation fails. Clinics are clogged with these patients, making it difficult to care for patients with real pathology. Making matters worse, patients often go from clinic to clinic until a diagnosis is made, leaving an incentive for physicians to make nominal diagnoses or risk losing patients. Indeed, a large study of the indications for spinal surgery in the mid-1980s showed that surgical decision making was often driven by duration and severity of pain and disability, patients’ illness behavior, and failure of conservative treatment.³⁴ As might be expected, the success rate for surgical treatment based on a nominal diagnosis is at best 30% to 40%. Interestingly, nearly every study in the past 50 years has shown that the presence of a psychiatric disease as an extremely poor predictor for good surgical outcome.^1,35–43 Thus, the responsible surgeon must use the history and physical examination to tease out signs of psychiatric imbalance and consider this carefully prior to proceeding with surgery.