Table 4. Logistic regression analysis of the relationship between decrease in tear secretion in VDT users and working duration.

Category	Sub category	Decrease in tear secretion (Schirmer score ≤5 mm)		OR† *	95% C I§
		Cases	Controls
		(n = 57)	(n = 544)
VDT working year	<4	8	170	reference
	4–8	11	119	1.84	0.69, 5.04
	8–12	18	148	2.49	1.02, 6.55
	≥12	20	107	3.61	1.39, 10.26
P trend = 0.012
Daily VDT hour	≤2	6	96	reference
	2–4	13	145	1.47	0.55, 4.39
	4–6	10	129	1.35	0.47, 4.23
	6–8	16	125	2.30	0.87, 6.89
	>8	12	49	4.27	1.47, 13.66
P trend = 0.005

†OR: odds ratio;

*Adjusted for gender and age;

§Confidence interval.