Repetitive stress injuries
Evidence suggests that about 3% of women and 2% of men will be diagnosed with carpal tunnel syndrome during their lifetime, 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 test results.
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%. On average, patients were about 48 years old. More than five times as many women then men participated in the study.
Older people are at higher risk than younger adults. CTS is very rare in children.
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 have carpal tunnel syndrome. The explanation for this greater risk is unknown, but it may be related to the smaller size of women's carpal tunnel.
Hormonal changes appear to play a major role in CTS.
In pregnant women, CTS may occur in both wrists. CTS that begins during pregnancy is not usually severe and persistent enough to require treatment. Although cases eventually go away on their own after delivery, symptoms may persist for 6 months or more.
CTS has also been shown to increase:
Women are also at a much higher risk for autoimmune disorders than men are; such disorders are significantly linked to CTS.
Being overweight consistently turns up as a risk factor for CTS and may play a direct causal role on CTS. Greater body mass appears to reduce nerve flow speed into the hand. Obesity is also related to poor physical fitness, which may also increase risk. A 2005 analysis indicated that weight is strongly linked to the onset of CTS in patients under the age of 63 years, but may be a less important factor as they get older.
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.
Computer Users and Typists. Repetitive typing and key entry has traditionally been associated with missing work due to CTS (as opposed to repetitive stress symptoms, which are unrelated to nerve impingement). 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.
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%, and as high as 10% in automobile workers.
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 2006 rating workers with highest to lowest total numbers of CTS-related events:
SOURCES: Bureau of Labor Statistics, U.S. Department of Labor, November 2006
Workers' Compensation and CTS. The issues surrounding workers' compensation are particularly troubling in determining accurately whether labor conditions cause carpal tunnel pain. CTS is a major contributor to workers' compensation cases.
Psychosocial Factors in the Workplace. Studies indicate that psychosocial factors in the workplace, such as intense deadlines, a poor social work environment, and low levels of job satisfaction, are major contributors to carpal tunnel pain. Such psychosocial conditions are more likely to be important factors in contributing to CTS in office workers, although they also complicate the condition in workers whose work is primarily physical.
At Home and 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.
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.
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.
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.
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