Epidemiological studies also point to certain risk factors that influence the incidence or prevalence of low back pain. These can be divided into two major groups: occupational and patient-related.
Hard labor and heavy exertions have been claimed as the cause of pain by more than 60% of patients with low back pain. Lifting, pulling and pushing, twisting, slipping, sitting for an extended period, and exposure to prolonged vibration, in isolation or in various combinations have been attributed to development of low back pain.
The likelihood of development of low back pain gradually increases up until approximately 55 years of age.
Men and women have similar risks of low back pain up until age 60. Thereafter, women are at greater risk, probably because of the development of osteoporosis.
There are no strong correlations among height, weight, body build, and low back pain. However, there is a higher risk of low back pain in very obese persons and possibly in tall persons.
The role of other postural changes such as kyphosis, increased or decreased lumbar lordosis, and discrepancy in the length of the lower limbs in the production of back pain has been subject to controversy.
Although these factors might contribute to back pain in some patients, no generally accepted hard evidence exists of a true association.
Most subjects with low back pain have at least some limitation of range of motion of the lumbar spine. One study found more pronounced reduction of flexibility of the lumber spin in subjects who went on to experience recurrence of low back pain during the year after the examination.
Several studies have shown decreased strength of abdominal and spinal muscles in patients with low back pain. Some studies have shown comparatively weaker back muscles, whereas others have shown comparatively weaker abdominal flexors.
SA study on Los Angeles Firefighters found that physical fitness and conditioning had a preventive effect on low back injuries. Another study found no difference in the rate of recovery from acute low back pain with improved physical fitness.
A recent study found no correlation between cardiovascular physical fitness and back strength in a group of healthy, normal women aged 29 to 40 years.
Persons who smoke seem to have an increased likelihood of development of low back pain. Smoking is known to increase the incidence of osteoporosis.
Depression, anxiety, hypochondriasis, hysteria, alcoholism, divorce, chronic headaches, and other factors have been reported with higher frequency in patients with chronic low back pain.
Whether these are the cause or the result of the low back pain is unclear. Most adults in the US will have low back pain at some time in their lives. As it stands, low back pain is the most frequent cause of lost work days in the US, surpassing the combination of acquired immunodifiency syndrome or AIDS, cancer, and stroke as a cause of disability among persons of working age.