Approximately 9–12% of people (632 million) have LBP at any given point in time, and nearly 25% report having it at some point over any one-month period.
About 40% of people have LBP at some point in their lives, with estimates as high as 80% among people in the developed world. Difficulty most often begins between 20 and 40 years of age. Men and women are equally affected. Low back pain is more common among people aged between 40 and 80 years, with the overall number of individuals affected expected to increase as the population ages.
Low back pain may be classified by duration as acute (pain lasting less than 6 weeks), sub-chronic (6 to 12 weeks), or chronic (more than 12 weeks). The condition may be further classified by the underlying cause as either mechanical, non-mechanical, or referred pain.
In most episodes of low back pain, a specific underlying cause is difficult to identify, with the pain believed to be due to mechanical problems such as muscle or joint strain.