Table 2.

Results From Modeling^a of Excess Odds Ratios for Cancers of the Oral Cavity, Pharynx, and Larynx According to Cigarette Smoking (Pack-Years and Cigarettes/Day), by Body Mass Index Category, Derived Using Case-Control Data From the International Head and Neck Cancer Epidemiology Consortium

Variable	Oral Cavity and Pharyngeal Cancer Cases and Controls						Laryngeal Cancer Cases and Controls
	Parameter Estimate			Effect Modification by BMIb			Parameter Estimate			Effect Modification by BMI
	βf	φ1f	φ2f	BMI Times:c	ΔDeviance (no.)d	P Valuee	βf	φ1f	φ2f	BMI Times:c	ΔDeviance (no.)d	P Valuee
Never Smokers and Current Smokers of Cigarettes Only
Total	0.0170	1.436	−0.270				0.2811	0.270	−0.025
BMI
<18.5	0.0184	2.889	−0.635	Both	0 (12)		67.30	−2.845	0.335	Both	0 (12)
18.5–24.9	0.3441	−0.262	0.006	Cigarettes/day	10.2 (9)	0.02	0.5546	−0.121	0.057	Cigarettes/day	18.9 (9)	<0.01
25.0–29.9	0.0003	3.647	−0.593	Pack-years	14.3 (6)	0.03	0.1238	0.925	−0.162	Pack-years	25.6 (6)	<0.01
≥30	0.0015	2.192	−0.345	None	72.5 (3)	<0.01	4.70 × 10−11	13.54	−1.942	None	29.7 (3)	<0.01
BMI (omitting <18.5)
18.5–24.9	0.3971	−0.334	0.017	Both	0 (9)		0.5783	−0.176	0.072	Both	0 (9)
25.0–29.9	0.0003	3.567	−0.581	Cigarettes/day	11.0 (7)	<0.01	0.1535	0.768	−0.132	Cigarettes/day	14.5 (7)	<0.01
≥30	0.0014	2.228	−0.347	Pack-years	8.3 (5)	0.08	3.64 × 10−9	13.68	−1.962	Pack-years	16.8 (5)	<0.01
				None	60.4 (3)	<0.01				None	18.8 (3)	<0.01
Never Smokers and Current Smokers of ≥10 Cigarettes/Day
Total	0.0019	2.779	−0.470				0.0004	4.314	−0.645
BMI
<18.5	0.4099	0.940	−0.388	Both	0 (12)		105.80	−2.615	0.220	Both	0 (12)
18.5–24.9	0.0027	2.758	−0.453	Cigarettes/day	0.9 (9)	0.82	0.0092	2.411	−0.327	Cigarettes/day	6.9 (9)	0.08
25.0–29.9	0.0004	3.388	−0.557	Pack-years	7.4 (6)	0.29	0.0001	5.138	−0.805	Pack-years	12.3 (6)	0.08
≥30	0.0103	1.093	−0.189	None	64.4 (3)	<0.01	7.70 × 10−11	13.19	−1.884	None	15.3 (3)	0.08
BMI (omitting <18.5)
18.5–24.9	0.0031	2.668	−0.440	Both	0 (9)		0.0092	2.383	−0.317	Both	0 (9)
25.0–29.9	0.0005	3.293	−0.541	Cigarettes/day	0.3 (7)	0.88	0.0001	5.114	−0.799	Cigarettes/day	5.8 (7)	0.06
≥30	0.0062	1.384	−0.229	Pack-years	0.5 (5)	0.98	6.85 × 10−8	13.27	−1.898	Pack-years	7.8 (5)	0.10
				None	52.5 (3)	<0.01				None	9.5 (3)	0.15

Abbreviations: BMI, body mass index; EOR, excess odds ratio.

^aModel: EOR = β_f d g_f (x), with g(x) = exp{φ₁ ln(x) + φ₂ ln(x)²}, where d is pack-years and x is cigarettes/day. The subscript (f) denotes separate effects for levels of BMI. Results were adjusted for study/center, education, age, sex, BMI, drink-years, and drinks/day.

^bWeight (kg)/height² (m²).

^cEffect modification of BMI by smoking, including: “both,” modification of BMI by pack-years and of BMI by cigarettes/day, β_f d g_f (x); “cigarettes/day,” modification of BMI by cigarettes/day, β d g_f (x); “pack-years,” modification of BMI by pack-years, β_f d g(x); and “none,” no effect modification, β d g(x).

^dDeviance change relative to the 12-parameter model β_f d g_f (x) and (in parentheses) number of parameters in the EOR.

^eP value from a likelihood ratio test relative to β_f d g_f (x), which included BMI modification for pack-years and cigarettes/day.