Table 3. Odds ratios of OL and OSF associated with betel quid chewing, Taiwan.

	Oral leukoplakia		Oral submucous fibrosis
Betel quid chewing/category	Cases/controls	ORa (95% CI)	Cases/controls	ORa (95% CI)	ORb ratio
Neverc	28/390	1.0	11/302	1.0
Ex	6/22	7.1 (2.3–21.5)	5/12	12.1 (2.8–51.9)
Current	91/88	22.3 (11.3–43.8)	78/62	40.7 (16.0–103.7)
Dose–response		4.6 (3.3–6.4)		6.2 (3.9–9.7)	1.3
Age first chewed (years)
⩾26	51/56	20.6 (9.9–42.7)	37/34	32.3 (12.1–86.6)
<26	46/54	19.5 (9.3–41.0)	46/40	39.4 (14.8–105.3)
Dose–response		4.3 (3.1–6.0)		5.8 (3.8–8.8)	1.3
Duration of chewing (years)
1–10	33/48	15.9 (7.1–35.6)		30.9 (11.3–84.7)
11–20	27/33	20.7 (8.9–48.2)	36/36	41.9 (14.1–124.9)
⩾21	37/29	24.0 (10.8–53.4)	28/25	39.3 (11.7–131.7)
Dose–response		3.0 (2.3–3.9)	19/13	4.2 (3.0–6.1)	1.4
Quantity of chewing (pieces/day)
1–10	53/73	16.6 (8.2–33.8)	41/42	31.4 (11.9–82.5)
11–20	24/25	21.0 (8.9–49.7)	24/21	37.4 (12.6–110.4)
⩾21	20/12	38.5 (14.1–105.1)	18/11	53.5 (16.4–174.8)
Dose–response		3.8 (2.8–5.1)		4.1 (2.9–5.8)	1.1
Cumulative pack-years
1–10	33/64	12.0 (5.6–25.7)	35/41	26.5 (10.0–70.3)
11–20	17/15	23.7 (9.1–61.7)	21/16	47.0 (15.8–139.8)
⩾21	47/31	31.4 (14.2–69.2)	27/17	51.4 (16.5–159.7)
Dose–response		3.1 (2.4–3.9)		4.1 (2.9–5.8)	1.3
Types of material
With betel inflorescence	60/56	24.5 (11.8–50.7)	47/38	38.7 (14.7–101.9)	1.6
With betel leaf	11/24	11.5 (4.2–32.0)	8/15	18.7 (5.3–66.1)	1.6
Mixed	26/30	17.4 (7.6–39.8)	28/21	37.4 (13.1–107.2)	2.1

^aOdds ratios were adjusted for education and occupation.

^bThe heterogeneity in ORs between OSF and OL was expressed as OR ratio.

^cNever chewers were a reference category.