Increase in carpal tunnel syndrome

The incidence of medically diagnosed carpal tunnel syndrome has increased dramatically during the past few decades, with the increase very rapid in the 1980s. However, according to the new report, contrary to what most would expect, the inflated rates are not due to work-related stress.

Carpal tunnel syndrome refers to pain, thumb muscle weakness and sensory changes in the hand. Where tendons and the nerve pass through the wrist to the hand, they thread through a canal in the wrist called the carpal tunnel. When the carpal tunnel becomes narrower as a result of inflammation of the surrounding tissue, the median nerve, causing tingling, numbness and pain in the thumb and index and middle fingers.

It appears that the most common cause of this inflammation is repetitive finger or hand movements that strain the wrist, for example typing, playing squash or weightlifting.

More common in women
Dr Russell Gelfman and colleagues from the Mayo Clinic in Rochester, Minnesota examined trends in the incidence of carpal tunnel syndrome; the use of surgical treatment; and work-related lost time between 1981 and 2005 among residents of Olmstead County, Minnesota, using the medical records from the Rochester Epidemiology Project and data from the Minnesota Department of Labour and Industry.

A total of 10 069 individuals were diagnosed with carpal tunnel syndrome in the study period. After accounting for the influence of age and gender, the incidence carpal tunnel syndrome was 376 per 100 000 persons per years. The incidence was significantly greater among women (491 vs 258 per 100,000 persons per years. Overall the annual rates increased nearly twofold over the study period, from 258 per 100,000 in the earlier period (1981 to 1985) to 424 per 100,000 people in the later period (2000 to 2005.)

"An increase in young, working-age individuals seeking medical attention for...less severe carpal tunnel syndrome in the early to mid-1980s was followed in the 1990s by an increasing incidence in elderly people," the investigators report.

Increased awareness
The increase in carpal tunnel syndrome incidence "was quite rapid in the 1980s and it would be difficult to attribute the causes for it solely to changes in medical or physical risk factors," Gellman said in an interview with Reuters Health. "We believe that increased awareness by the public, in particular the publicity resulting from the epidemic of work-related carpal tunnel syndrome, may explain some of the trend," he said.

"We also found that the trend started with younger people in the early years of the study, but in the later times, the number of elderly presenting for care increased," Gellman said. "In comparison to younger people, the elderly presented with more severe disease and were more likely to require surgery."

While the average annual incidence of carpal tunnel release surgery was 109 per 100 000, the incidence of surgery for work-related carpal tunnel syndrome was only 11 per 100 000, according to the report.

If the trend in the elderly continues, "we might expect the number of operations and associated expenditures for carpal tunnel syndrome to increase as our population ages," Gellman added. "The study also raises questions about the underlying reasons for the trend of decreasing incidence in work-related carpal tunnel syndrome, even though it was increasing in the general population." – (Michelle Rizzo/Reuters Health)

SOURCE: Neurology, January 6, 2009.

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Carpal Tunnel Syndrome

January 2009