Epidemiology of low back pain.

Low back pain is a symptom that cannot be validated by an external standard. It is a disorder with many possible etiologies, occurring in many groups of the population, and with many definitions. Low back pain is a common problem, with a prevalence in the United States ranging from 8% to 56%. It is estimated that 28% experience disabling low back pain sometime during their lives, 14% experience episodes lasting at least 2 weeks, 8% of the entire working population will be disabled in any given year, and the lifetime prevalence of low back pain is 65% to 80%. It is believed that most episodes of low back pain will be short-lived and that 80% to 90% of attacks of low back pain resolve in about 6 weeks, irrespective of the administration or type of treatment. However, multiple studies in the late 90s showed recurrent or chronic low back pain, evaluated at 3 months, 6 months, or 12 months, ranging from 35% to 79%. Risk factors of low back pain are multifactorial, with many possible etiologies. Multiple risk factors of low back pain and lower-extremity pain include physical factors, social demographic characteristics, habits, and psychosocial factors. This review will discuss the epidemiology of low back pain, with emphasis on frequency, causes, and consequences of low back pain; the influence of age, gender, morphologic characteristics, and genetics; and the influence of occupational, mechanical, social, habitual, and psychological factors.