Associations between selected workplace biomechanical exposures and incident carpal tunnel syndrome stratified by (A) repetition, (B) peak hand force, or (C–E) years worked at time of enrolment
| Cohort (N) | Cases (n) | HR | 95% CI | |
|---|---|---|---|---|
| (A) Analyst-rated peak hand force stratified by total hand repetition rate | ||||
| Analyst peak force: subgroup with ≤18.1 repetitions/min | 1100 | 82 | ||
| Lower tertile | 35 | 1.00 | ||
| Middle tertile | 27 | 1.03 | 0.60 to 1.77 | |
| Upper tertile | 20 | 1.82 | 0.99 to 3.37 | |
| Analyst peak force: subgroup with >18.1 repetitions/min | 1033 | 71 | ||
| Lower tertile | 14 | 1.00 | ||
| Middle tertile | 38 | 2.78 | 1.51 to 5.14 | |
| Upper tertile | 19 | 2.97 | 1.41 to 6.27 | |
| (B) Total hand repetition rate stratified by analyst-rated peak hand force | ||||
| Total repetition rate: subgroup with lower peak hand force (≤3) | 1308 | 91 | ||
| Lower tertile | 36 | 1.00 | ||
| Middle tertile | 29 | 1.01 | 0.59 to 1.73 | |
| Upper tertile | 26 | 1.11 | 0.60 to 2.07 | |
| Total repetition rate: subgroup with higher peak hand force (>3) | 878 | 62 | ||
| Lower tertile | 21 | 1.00 | ||
| Middle tertile | 27 | 1.36 | 0.76 to 2.44 | |
| Upper tertile | 14 | 0.64 | 0.30 to 1.37 | |
| (C) Analyst-rated peak hand force stratified by years worked at enrolment | ||||
| Analyst peak hand force: subgroup with <3 years of work | 674 | 37 | ||
| Lower tertile | 10 | 1.00 | ||
| Middle tertile | 16 | 1.83 | 0.80 to 4.17 | |
| Upper tertile | 11 | 3.37 | 1.16 to 9.81 | |
| Analyst peak hand force: subgroup with ≥3 years of work | 1345 | 113 | ||
| Lower tertile | 39 | 1.00 | ||
| Middle tertile | 46 | 1.46 | 0.94 to 2.28 | |
| Upper tertile | 28 | 1.88 | 1.12 to 3.18 | |
| (D) Forceful hand repetition rate stratified by years worked at enrolment | ||||
| Forceful repetition rate: subgroup with <3 years of work | 727 | 40 | ||
| Lower tertile | 12 | 1.00 | ||
| Middle tertile | 17 | 2.18 | 0.97 to 4.89 | |
| Upper tertile | 11 | 2.78 | 0.93 to 8.27 | |
| Forceful repetition rate: subgroup with ≥3 years of work | 1608 | 123 | ||
| Lower tertile | 45 | 1.00 | ||
| Middle tertile | 39 | 1.45 | 0.93 to 2.28 | |
| Upper tertile | 39 | 1.75 | 1.07 to 2.86 | |
| (E) % duration forceful hand exertion stratified by years worked at enrolment | ||||
| % duration forceful exertions: subgroup with <3 years of work | 727 | 40 | ||
| Lower tertile | 11 | 1.00 | ||
| Middle tertile | 17 | 1.94 | 0.86 to 4.40 | |
| Upper tertile | 12 | 2.53 | 0.90 to 7.09 | |
| % duration forceful exertions: subgroup with ≥3 years of work | 1608 | 123 | ||
| Lower tertile | 44 | 1.00 | ||
| Middle tertile | 34 | 1.32 | 0.83 to 2.12 | |
| Upper tertile | 45 | 2.16 | 1.36 to 3.43 | |
All models are adjusted for age, gender, body mass index, study site and the other biomechanical variables listed in table 3.