Table 4.

Results of logistic regression analysis by a stepwise method

Independent variable	P-value	Odds ratio	95% confidence interval
Gender: male	0.001	1
: female		1.62	1.21–2.17
PC usage	0.005
0.1 h increments		1.04	1.00–1.08
1.0 h increments		1.49	1.44–1.55
2.0 h increments		2.23	2.14–2.31