Risk Factors
Evidence suggests that about 3% of women and 2% of men will be diagnosed with carpal tunnel syndrome during their lifetimes, with peak prevalence in women older than 55. Still, determining how many people actually have CTS is very difficult. Many people report CTS symptoms who have normal test results and some people have no symptoms and show abnormal results. Furthermore, there is some evidence that after a decline in cases, the prevalence in CTS is rising.
Age
Older people are at higher risk than younger adults are. It is very rare in children.
Women
Many studies indicate that women have a significantly higher risk for carpal tunnel syndrome than men do. According to the National Institutes of Health, women are three times more likely than men to experience carpal tunnel syndrome. The explanation for this greater risk is unknown but may be related to the smaller size of women's carpal tunnel.
Hormonal changes appear to play a major role as evidenced by an increased incidence in CTS symptoms during the following hormone-related events:
- During pregnancy. According to one small 2001 study, most cases occurred in the third trimester and weight gain increased the risk. In another study, CTS developed at any point during the pregnancy. New-onset CTS during pregnancy that is severe and persistent enough to require treatment is uncommon, however. Most cases resolve spontaneously after delivery. (In one study, 11% of women reported CTS six months after delivery and 4.3% still had the condition a year afterward.)
- During the postpartum period.
- At the time of menopause.
- Breast feeding, which temporarily lowers natural steroid hormone levels, has been linked to flare-ups of inflammatory disorders such as CTS.
Other conditions that are more specific to women than men may increase the risk for carpal tunnel syndrome:
- The hand-intensive nature of housework and typing may contribute to a higher incidence in women.
- Women are also at significantly higher risk for autoimmune disorders than men are; such disorders are highly linked to CTS.
Family History
People with close relatives who have carpal tunnel have a higher risk themselves. This risk may be due to a family histories of medical conditions associated with CTS, obesity, or genetic factors.
People with Underlying Medical Conditions
A number of illnesses, skeletal abnormalities, and injuries can predispose individuals to carpal tunnel syndrome, including autoimmune diseases and arthritic conditions.
Workers at High Risk
At high risk are those whose occupations combine force and repetition of the same motion in the fingers and hand for long periods.
Specific Workers at Risk for CTS
Virtually all workers who use their hands and wrists repetitively are at risk for CTS, particularly if they work in cold temperatures and have factors or medical conditions that make them susceptible.
Notes on Specific Occupations Associated with CTS
Computer Users and Typists. Repetitive typing and key entry is highly associated with missing work due to CTS. The risk for CTS in this group, however, is still much lower than with occupations involving heavy labor. Although more than 10% of the computer users complain of CTS symptoms, the evidence implicating computer use as a major cause of CTS is weak. One small 2001 study reported that nerve conduction tests on frequent computer users showed the same rate of CTS (3.5%) as in the general population. A 2003 study found an association between mouse-use (not keyboard use) and CTS. The typing speed may affect risk, in some case, however. For example, the fingers of typists whose speed is 60 words per minute exert up to 25 tons of pressure each day. And in one study, typists with CTS struck the keys with greater force than those without the disorder.
Meatpackers and Other Very High Risk Workers. Workers in the meat and fish packing industries and those who assemble airplanes have the highest risk for CTS, according to one study. Meat packers complained of pain and loss of hand function as long ago as the 1860's. Even today, the incidence of carpal tunnel syndrome in the meat, poultry, and fish packing industries may be as high as 15%.
Musicians. Musicians are at very high risk for CTS and other problems related to the muscles and nerves in the hands, upper trunk, and neck. In one study, 20% reported CTS or other nerve disorders in the hands and wrists.
Highest to Lowest Numbers of CTS Events by Job
The following is a list of occupations published by the Bureau of Labor Statistics in 2002 that rates workers with highest to lowest total numbers of CTS-related events:
- Assemblers
- Cashiers
- Secretaries
- General office clerks
- Laborers, nonconstruction
- Bookkeepers, accounting, and auditing clerks
- Welders and cutters
- Data-entry employees
- Textile sewing machine operators
- Order clerks
- Supervisors and proprietors, sales occupations
- Machine operators (unspecified)
- Truck drivers
- Investigators and adjusters (i.e., insurance)
- Insurance adjusters, examiners, and investigators
- Electrical and electronic equipment assemblers
- Packaging and filling machine operators
- Janitors and cleaners
- Bank tellers
- Production inspectors, checkers, and examiners
SOURCES: Bureau of Labor Statistics, U.S. Department of Labor April 2002
At Home
People who intensively cook, knit, sew, or do needlepoint, play computer games, do carpentry, or extensively use power tools.
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Obesity and Other Physical Characteristics
Obesity. Obesity is highly linked with carpal tunnel syndrome.
Square Wrists. Some (but not all) studies have reported a higher risk for CTS in people square wrists (the thickness and width are about the same) than in those with the more common rectangular wrists.
Palm Shape. In one study, patients with palms that were both shorter- and wider-than-average and who also had shorter third fingers were more likely to have CTS than those without these hand characteristics.
Poor Upper Back Strength. Some researchers claim that poor upper back strength makes people more susceptible to poor posture and injuries in the upper extremities, including carpal tunnel syndrome.
Smoking and Alcohol Abuse
Cigarette smoking slows down blood flow, so that smokers have worse symptoms and slower recovery than nonsmokers do. Increased alcohol intake has been associated with CTS in people with other risk factors.
Other Factors
Poor nutrition, previous injuries, and stress can increase one's risk for carpal tunnel syndrome.
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