Table 2. Cox proportional hazard regression models in analyzing OL malignant transformation risk.

Variables	p value	Hazard ratio	95% CI
Univariate analysis
Age (≤55 v>55)	0.721	0.859	0.372–1.981
Sex (male v female)	0.061	0.406	0.158–1.044
Grade of dysplasia (L–M v H)*	0.032	0.394	0.168–0.923
Lesion site (tongue v nontongue)	0.514	0.753	0.322–1.764
Smoking (negative v positive)	0.199	2.603	0.605–11.199
Alcohol intake (negative v positive)	0.514	1.503	0.442–5.103
SMAD4 expression (weak v strong)	0.018	0.298	0.110–0.810
Multivariate analysis
Grade of dysplasia (L–M v H)	0.021	0.367	0.157–0.861
SMAD4 expression (weak v strong)	0.013	0.282	0.104–0.769

CI: confidence interval.

^*L–M: low and moderate-grade dysplasia, H: high-grade dysplasia.

Bold indicates values that are statistically significant (p<0.05).