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 and have normal test results. Other people have no symptoms and abnormal results. Furthermore, some evidence suggests that, after an apparent a decline in cases, the prevalence of CTS is rising.

A large 2005 study of more than 1,000 patients found that the severity of CTS was mild in 42% of patients, moderate in 18%, and severe in 40%. Patients were an average of about 48 years old. More than five times as many women then men participated in the study.

Age

Older people are at higher risk than younger adults. 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 in CTS.

A 2005 study reported that 17% of pregnant women had CTS. Nearly one-quarter of those had it in both wrists. Early studies have presented conflicting reports regarding when CTS is most likely to occur during pregnancy. One found that most cases occurred in the third trimester, and weight gain increased the risk. Another concluded that CTS developed at any point during the pregnancy. New-onset CTS during pregnancy that is severe and persistent enough to require treatment is uncommon. Most cases go away on their own after delivery. However, in one study, 11% of women reported CTS six months after delivery, and 4.3% of them still had the condition a year afterward.

Breastfeeding has also been linked to flare-ups of inflammatory disorders such as CTS. Breastfeeding temporarily lowers the level of natural steroid hormones.

CTS has also been shown to increase during:

  • The postpartum period
  • Menopause

Other conditions that are more specific to women than men may increase their risk for carpal tunnel syndrome:

  • The hand-intensive nature of housework and typing may contribute to a higher incidence of CTS in women.
  • Women are also at a much higher risk for autoimmune disorders than men are; such disorders are significantly linked to CTS.

Family History

People with close relatives who have carpal tunnel syndrome have a higher risk of developing CTS themselves. This risk may be due to 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. Typing speed may affect risk in some cases, however. For example, the fingers of typists whose speed is 60 words per minute exert up to 25 tons of pressure each day. In one study, typists with CTS struck the keys with greater force than those without the disorder. A large Danish study showed no increased risk of CTS among people who use computers at work. Another study of workers who used computers heavily (up to 7 hours per day) found no increased risk of CTS among them.

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 1860s. Even today, the incidence of carpal tunnel syndrome in the meat, poultry, and fish packing industries may be as high as 15%. A 2005 study of automobile assembly workers found that the estimated annual rate of CTS ranged from 1% to 10%.

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 rating workers with highest to lowest total numbers of CTS-related events:

  • Assemblers
  • Cashiers
  • Secretaries
  • General office clerks
  • Laborers, non-construction
  • 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
  • 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 and At Play

People who intensively cook, knit, sew, do needlepoint, play computer games, do carpentry, or extensively use power tools are at increased risk for CTS. Long-distance cycling may make symptoms of carpal tunnel syndrome worse.

Other Physical Characteristics

Square Wrists. Some (but not all) studies have reported a higher risk for CTS in people with 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. In addition, high levels of so-called “bad” cholesterol (low-density lipoprotein, or LDL) have also been linked to an increased risk of CTS.

Review Date: 4/1/2006
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital