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 discs begin deteriorating and growing thinner by age 30. One-third of adults over 20 show evidence of herniated discs (although only 3% of these discs cause symptoms). As people continue to age and the discs 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 Discs. 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 disc to be less able to resist compressive forces. One 2001 study found the defective gene was present in twice as many patients with disc problems as in patients without back pain.
Central Nervous System Abnormalities and Changes in Pain Perception
Some evidence suggests that after episodes of back pain, some people may experience changes in the brain that produces an exaggerated response in nerve cells and other factors. Such activity causes a persistent perception of pain even though the actual injury has healed.
Psychological and Social Factors
Although disc abnormalities are certainly a cause of low back pain, many people with disc rupture or tears do not experience back pain. And some people without disc 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 abnormalities in some people who have abnormal discs. 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.
- 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.
Studies also suggest that patients who reported prolong emotional distress have less favorable outcomes after back surgeries. It should be strongly noted that the presence of psychological factors in no way diminishes the reality of the pain and its disabling effects. Recognizing it as a strong player in many cases of low back pain, however, can help determine the full range of treatment options.
Pregnancy
Pregnant women are prone to back pain due to a shifting of abdominal organs, the forward redistribution of body weight, and the loosening of ligaments in the pelvic area as the body prepares for delivery. Tall women are at higher risk than short women. Although some earlier research had suggested that the use of epidurals for pain relief during labor could lead to chronic back pain, studies in 2002 reported no increased risk.
Infections and Other Medical Conditions
Infections. A number of common and uncommon infections are a cause of back pain. Chronic uterine or pelvic infections can cause low back pain in women. Osteomyelitis is infection in the spine, a rare cause of back pain. Other infections that cause back pain include Lyme disease, septic arthritis, bacterial endocarditis, Reiter's syndrome, mycobacterial and fungal arthritis, and viral arthritis. Chlamydia pneumonia, an atypical organism that is a common cause of mild pneumonia in young adults, is now believed to cause widespread inflammation in the body's tissue, including blood vessels, and may be responsible for a number of chronic conditions, including heart disease. Some evidence further suggests it may cause inflammation in arteries of the lower spine and contribute to spinal stenosis.
Common Medical Conditions. Many other medical conditions are associated with back pain.
- Osteoporosis is a disease of the skeleton in which the amount of calcium present in the bones slowly decreases to the point where the bones become fragile and prone to fracture. It usually does not cause pain unless the vertebrae collapse suddenly, in which case the pain is often severe. Studies indicate, however, that the incidence of low back pain and sciatica increase around the time of menopause, and very tiny fractures in the vertebrae caused by osteoporosis may be an undetected cause of back pain in many elderly women.
- Osteoarthritis occurs in joints where cartilage is damaged and then destroyed, usually as a result of aging. In reaction to this destruction, the bones associated with the joints develop abnormalities. When osteoarthritis affects the spine, it may damage the cartilage in the discs, the moving joints of the spine, or both. The nerves may become pinched, causing pain and in advanced cases, numbness and muscle weakness. The patient may also experience muscle spasms and diminished mobility.
- Inflammatory disorders, such as Crohn's disease and rheumatoid arthritis, can produce inflammation in the spine (sacroiliitis), although the spine is less commonly affected than other locations.
- Other conditions that can directly cause pain include fibromyalgia, Paget's disease, or Parkinson's disease, abscesses, blood clots, and cancer.
- Others medical conditions cause referred back pain, which occurs in conjunction with problems in organs unrelated to the spine (although usually located near it). Such conditions include ulcers, kidney disease (including kidney stones), ovarian cysts, and pancreatitis.
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| Osteoporosis is a condition characterized by progressive loss of bone density, thinning of bone tissue and increased vulnerability to fractures. Osteoporosis may result from disease, dietary or hormonal deficiency or advanced age. Regular exercise and vitamin and mineral supplements can reduce and even reverse loss of bone density. |
It should be noted, however, that a number of medical conditions, such as lung and heart problems and chronic headaches, commonly occur with low back pain, but a causal relationship is uncertain.
Muscular Abnormalities
Some research is suggesting that some people have motor control abnormalities in the deep muscles near the spine. Such lack of control causes instability in the spine that can lead to pain.
Medications
Medications may trigger back pain. For example, anticoagulants can cause bleeding or an internal bruise. Long-term steroid use can cause infection or compression fractures.
Conditions That Cause Back Pain in Children
Persistent low back pain in children is more likely to have a serious cause that requires treatment than back pain in adults. According to one small study, one third of children being treated at a hospital for back pain were found to have serious underlying problems. Among the conditions that cause back pain in children are the following:
- Stress fractures (spondylolytis) in the spine, is a common cause of back pain in young athletes. (Sometimes a fracture may not show up for a week or two after an injury.) It can cause spondylolisthesis, in which the spine becomes unstable and the vertebrae slip over each.
- Hyperlordosis is an inborn exaggerated inward curve in the lumbar area. (Scoliosis, an abnormal curvature of the spine in children, does not usually cause back pain.)
- Injuries.
- Benign tumors (e.g., osteoblastoma or neurofibroma).
- Cancers, including leukemia.
- Juvenile chronic arthropathy is an inherited form of arthritis. It can cause pain in the sacrum and hip joints of children and young people. It used to be grouped under juvenile rheumatoid arthritis, but is now defined as a separate problem.
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