Repetitive tasks and heavy lifting performed at work in 1984 had an inverse relationship to the development of carpal tunnel syndrome over the subsequent 17 years in a prospective study performed by Nathan et al. Physical work factors, aggregated in value between 1984 and 1994/1995, were not predictive of being a 2001/2002 case of carpal tunnel syndrome. Female gender and higher body mass index were associated with carpal tunnel syndrome in both analysis methods.
In 1984, 471 industrial sector workers volunteered information about personal factors (age, gender, body mass index, endocrine condition, and cigarette smoking) and physical work factors (exposure to heavy lifting, vibration, keyboard use, repetition, and force). Work factors were rated on a scale of 1 to 5 where 1 meant not at all and 5 meant consistent. Personal factors were reassessed in 1989, 1994/1995, and 2001/2002 follow-ups. Work factors were reviewed in the 1989 and 1994/95 follow-ups and given an aggregate value due to changes in work tasks.
A case of carpal tunnel syndrome was defined as a combination of:
* the report of two or more hand/wrist symptoms specific to CTS (numbness, tingling and nocturnal awakening) at least twice per month or, the report of one symptom specific to CTS at least twice per month and two or more hand/wrist symptoms indirectly related to CTS (pain, tightness, and clumsiness) at least twice per month
* median nerve conduction maximum latency difference of .40 ms or greater
The study compared the 1984 worker characteristics (personal and work factors) to the development of carpal tunnel syndrome revealed at subsequent evaluations in 1989, 1994/1995, and 2001/2002. Analysis was also made between the aggregate value of personal and work factors collected in 1984, 1989, 1994/1995 and a case of carpal tunnel syndrome identified in 2001/2002.
Greater age and exposure to vibration and force in 1984 were moderately associated with the development of carpal tunnel syndrome over the subsequent 17 years. Greater age and aggregate heavy lifting value were moderately related to 2001/2202 carpal tunnel syndrome cases.
Subjects were hard to follow over the 17 years. Of the original 471 participants in 1984, 316 were found in 1989, 289 in 1994/1995, and 167 in 2001/2002 (which became restricted to 148 for data analysis). The authors acknowledged that the drop in participants from the original subject pool (2001/2002 analysis consisted of 31 percent of the 1984 group) may have influenced their findings.
Further, Nathan et al. noted their conclusions are in opposition to other research that associates physical work factors with carpal tunnel syndrome. It was suggested that since job tasks are changed over time, physical work factors may receive undue emphasis compared to personal risk factors which are present long term relative to CTS development.
Article Title: A Longitudinal Study of Predictors of Research-Defined Carpal Tunnel Syndrome in Industrial Workers: Findings at 17 Years
Publication: Journal of Hand Surgery (British and European Volume) 30B: 6:593-598, 2005
Authors: P A Nathan, J A Istvan and K D Meadows
This article originally appeared in The Ergonomics Report™ on 2006-03-29.