Table 1. Summarized, stratified data of age at diagnosis, anatomic tumor site, and sex and associations among the grade of tumor cell differentiation and habits of smoking, betel nut chewing, and alcohol consumption.

		Grade
		Grade 1 (n = 435)		Grade 2 (n = 1964)		Grade 3 (n = 136)		Total (n = 2535)		p-value
		N	%	N	%	N	%	N	%
Age at diagnosis	≤40	15	3.4	137	7.0	11	8.1	163	6.4	<0.001
	41–50	75	17.2	434	22.1	37	27.2	546	21.5
	51–60	156	35.9	701	35.7	48	35.3	905	35.7
	61–70	127	29.2	448	22.8	20	14.7	595	23.5
	≧71	62	14.3	244	12.4	20	14.7	326	12.9
Site of tumors	Alveolar ridge	71	16.3	328	16.7	16	11.8	415	16.4	<0.001
	Anterior tongue	82	18.9	587	29.9	52	38.2	721	28.4
	Buccal mucosa	193	44.4	659	33.6	39	28.7	891	35.1
	Hard palate	16	3.7	53	2.7	4	2.9	73	2.9
	Floor of mouth	3	0.7	67	3.4	7	5.1	77	3.0
	Retromolar trigone	15	3.4	110	5.6	7	5.1	132	5.2
	Mucosa of the Lips	55	12.6	160	8.1	11	8.1	226	8.9
Gender	Female	12	2.8	98	5.0	9	6.6	119	4.7	0.076
	Male	423	97.2	1866	95.0	127	93.4	2416	95.3
Smoking	No	97	26.6	418	25.8	28	23.9	543	25.8	0.839
	Yes	267	73.4	1204	74.2	89	76.1	1560	74.2
	Unknown							432
Betel nut	No	171	47.0	687	42.4	48	41.0	906	43.1	0.246
	Yes	193	53.0	935	57.6	69	59.0	1197	56.9
	Unknown							432
Alcohol	No	183	56.0	714	49.7	47	46.1	944	50.6	0.079
	Yes	144	44.0	723	50.3	55	53.9	922	49.4
	Unknown							669

p-value by chi-square test. Regarding sex, p trend = 0.024In the alcohol group, p trend = 0.027.

Grade 1: well differentiated; Grade 2: moderately differentiated; Grade 3: poorly differentiated.

In the smoking and betel nut groups, 432 cases were excluded due to incomplete data.

In the alcohol group, 669 cases were excluded due to incomplete data.