Carpal tunnel syndrome (CTS) is a common cause of disability, but its causes remain unknown. Although the role of occupational factors has been the focus of much research, numerous investigations have shown that risk of CTS may also be elevated by factors such as female gender, overweight, cigarette smoking, and endocrine disorders. However, many findings have been limited by a focus on cross-sectional investigation of individuals with pre-existing CTS. Because causality can be most clearly established by longitudinal investigation of an initially healthy cohort, we initiated a longterm study of predictors of carpal tunnel syndrome in industrial workers in the Portland, Oregon area in 1984. The present report is an analysis of findings through seventeen years of follow-up.

METHOD. 471 workers were examined at baseline in 1984, and 316 and 289 re-examined in 1989 and 1994-95, respectively. Virtually all procedures were completed at the worksite. In 2001-2002 we attempted to re-contact the 1994-95 participants for a follow-up exam at our clinic. One hundred and sixty eight participants completed the follow-up examination, and 27 provided a telephone interview only. The remaining loss to follow-up was primarily a consequence of residence outside of the Portland area, refusal, or an inability to locate. The focus of these analyses was on the 148 participants who were CTS-free in 1984.

At all points, a case definition of CTS was based on both median nerve abnormality as determined by electrophysiologic testing and specific patterns of symptom report. Other assessments included a medical history, ratings of workplace activities and lifestyle factors such as body weight, cigarette smoking, and recreational physical activity.

RESULTS. Returning participants averaged 53.49 years of age. Fifty-seven per cent were male and 43% were female. Body mass index averaged a relatively high 30.80, within a range generally considered obese.

In logistic regression analyses, we examined the relationship of both personal factors (age, gender, relative obesity, and cigarette smoking) and occupational activities (use of vibratory tools, or repetitive or forceful hand use) to prevalent dominant hand CTS. In this relatively small sample, CTS was significantly related to female gender and greater body weight, but unrelated to occupational activities, age, or cigarette smoking.

CONCLUSIONS. These findings offer support for the role of relative overweight in carpal tunnel syndrome. Because of the societal and personal costs associated with disability from CTS, further longitudinal investigation of factors associated with CTS etiology seems long overdue.