Risk Factors

Risk Factors

In most known cases, pain begins with an injury, after lifting a heavy object, or after making an abrupt movement. Not all people experience back pain after such events, however. A number of conditions may make people more or less susceptible to low back pain. In 85% of back pain cases, the causes are unknown.

Aging Process

Intervertebral disks begin deteriorating and growing thinner by age 30. One-third of adults over 20 show evidence of herniated disks (although only 3% of these disks cause symptoms). As people continue to age and the disks lose moisture and shrink, the risk for spinal stenosis increases. The incidence of low back pain and sciatica increases in women at the time of menopause as they lose bone density. In older adults, osteoporosis and osteoarthritis are also common. However, the risk for low back pain does not mount steadily with ever-increasing age, which suggests that at a certain point, the conditions causing low back pain plateau.

Genetic Factors

Inherited Spinal Structure Abnormalities. Many people have a genetic susceptibility to low back pain, usually from inheriting spinal structural abnormalities.

Inherited Weakened Disks. Studies are finding that specific mutations of the COL9A gene may play a role in about 10% of sciatica cases. The gene is normally involved in producing collagen, the protein building block in all structural tissue in the body. When defective, it may cause the disk to be less able to resist compressive forces. One 2001 study found the defective gene was present in twice as many patients with disk problems as in patients without back pain.

The Brain and Pain Perception

Some evidence suggests that after episodes of back pain, some people may experience changes in brain structure and chemicals that produce an exaggerated response in nerve cells. In fact, a 2005 study suggested that chronic back pain actually shrinks the brain by as much as 11%. Such brain changes may cause a persistent perception of pain even though the actual injury has healed.

Psychological and Social Factors

Although disk abnormalities are certainly a cause of low back pain, many people with disk rupture or tears do not experience back pain. And some people without disk abnormalities complain of back pain. Psychological factors are known to play a strong influential role in three phases of low back pain:

• Onset of pain. Some evidence suggests preexisting depression and the inability to cope may be more likely to predict the onset of pain than physical problems. For example, a British study reported that people who showed emotional distress at age 23 were nearly twice as likely to suffer from back pain ten years later. A 2005 study found that a “passive” coping style (not wanting to confront problems) was strongly associated with the risk of developing disabling neck or low back pain.
• The perception of pain. Social and psychological factors play a role in the severity of a person's perception of back pain. For example, one study compared truck drivers and bus drivers. Nearly all the truck drivers liked their work. Half of them reported low back pain but only 24% lost time at work. Bus drivers, on the other hand, reported much lower job satisfaction than truck drivers, and these workers with back pain had a significantly higher absentee rate than truck drivers in spite of less stress on their backs. Similarly, another study found that pilots, who generally reported "loving their jobs," reported far fewer back problems than their flight crews. And yet another study reported that low rank, low social support, and high stress in soldiers was associated with a higher risk for disabling back pain.
• Chronic pain. Depression and a tendency to develop physical complaints in response to stress also increase the likelihood that acute back pain will become a chronic condition. The way a patient perceives and copes with pain at the beginning of an acute attack may actually condition the patient to either recover or develop a chronic condition. Those who over-respond to pain and fear for their long-term outlook tend to feel out of control and become discouraged, increasing their risk for long-term problems.