Differences in risk factors for neurophysiologically confirmed carpal tunnel syndrome and illness with similar symptoms but normal median nerve function: a case–control study

Table 4 Associations with occupational risk factors according to neurophysiological findings

Risk factor	Controls	NP+ve cases^a			NP-ve cases^a
	n^a	n^a	OR^b	(95% CI)	n^a	OR^b	(95% CI)
Physical activities in an average working day ^c
Use of keyboard or mouse for > 4 hours in total	254	120	0.7	(0.6-1.0)	145	1.1	(0.9-1.5)
Other repeated movements of wrist/fingers for > 4 hours in total	312	246	1.7	(1.3-2.1)	203	1.5	(1.2-1.9)
Repeated bending /straightening of elbow for > 1 hour in total	416	293	1.5	(1.2-1.9)	254	1.4	(1.1-1.8)
Work for >1 hour in total with tool(s) that made the hand(s) or arm(s) vibrate	60	77	2.6	(1.8-3.9)	52	1.8	(1.2-2.7)
Work with hand above shoulder height for > 1 hour in total	91	86	1.8	(1.3-2.5)	58	1.2	(0.9-1.8)
Lifting/carrying weights ≥ 5 kg in one hand	285	195	1.3	(1.0-1.6)	160	1.1	(0.9-1.5)
Work with neck bent forward for >2 hours in total	296	193	1.2	(0.9-1.5)	176	1.3	(1.0-1.7)
Work with neck twisted for > 0.5 hours in total	181	125	1.3	(1.0-1.6)	101	1.1	(0.8-1.5)
Psychosocial risk factors ^c
Targets, bonuses or deadlines	419	247	1.0	(0.8-1.2)	207	0.9	(0.7-1.1)
Little support from supervisor or colleagues	82	78	1.7	(1.2-2.4)	78	2.0	(1.5-2.9)
Little choice in how or what work is done or in timetable and breaks	137	116	1.6	(1.2-2.1)	96	1.6	(1.2-2.1)
Job dissatisfaction	90	59	1.1	(0.8-1.5)	62	1.3	(0.9-1.9)

^aAnalyses were restricted to 1628 subjects (773 controls, 457 NP+ve cases and 398 NP-ve cases) who had held a paid job. Data on some risk factors were missing for small numbers of cases and/or controls.
^bAdjusted for sex, age (in 10-year strata) and ethnicity.
^cRisk estimates are for those exposed to the risk factor relative to those unexposed.

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