Chronic low back pain: epidemiology, economic burden and patient-reported outcomes in the USA.

Chronic low back pain is identified by the length of time a patient suffers from low back pain, the location of the pain and the etiology of the symptoms. Approximately 5-10% of patients with low back pain develop chronic low back pain that lasts longer than 3 months. There has been no consensus regarding the definition of low back pain; therefore, there is a wide variation in the prevalence estimates reported in the literature. Commonly used drugs for chronic low back pain include antidepressants, analgesics, antiepileptic drugs and muscle relaxants. In the USA, back pain is one of the most frequent reasons for hospitalization and physician visits, resulting in high medical care costs.