Table 3.

Estimated Elevation in Brain Tumor Risk^a for Regular Mobile Phone Users With Information on Preferred Side of Use^b (n = 792) From Stratified Models, INTERPHONE Grid Data, 2000–2004

Covariate	No. of Tumorsc	Distance From Preferred Ear to Gravity Center of Tumor, mm										P Valuee
		0–55		55.01–75		75.01–95		95.01–115		≥115.01d
		${\stackrel{\mathbf{ˆ}}{\mathbf{\alpha }}}_{\mathbf{1}}$	95% CI	${\stackrel{\mathbf{ˆ}}{\mathbf{\alpha }}}_{\mathbf{2}}$	95% CI	${\stackrel{\mathbf{ˆ}}{\mathbf{\alpha }}}_{\mathbf{3}}$	95% CI	${\stackrel{\mathbf{ˆ}}{\mathbf{\alpha }}}_{\mathbf{4}}$	95% CI	$\stackrel{\mathbf{ˆ}}{\mathbf{\alpha }}$	95% CI
Sex												0.26
Female	284	1.85	1.41, 4.04	1.85	1.36, 2.96	1.71	1.17, 2.44	1.00	1.00, 1.41	1.00	N/A
Male	508	3.04	1.63, 7.54	1.68	1.26, 2.33	1.31	1.00, 1.78	1.21	1.00, 1.64	1.00	N/A
Age, years												0.39
≤46	379	1.86	1.45, 4.37	1.86	1.38, 2.76	1.54	1.10, 2.09	1.00	1.00, 1.34	1.00	N/A
>46	413	3.06	1.63, 7.29	1.69	1.25, 2.51	1.40	1.03, 1.98	1.36	1.00, 1.91	1.00	N/A
Tumor gradef												0.54
1 or 2	331	2.59	1.45, 6.61	1.82	1.25, 2.75	1.15	1.00, 1.76	1.15	1.00, 1.68	1.00	N/A
3 or 4	417	2.16	1.46, 5.01	1.64	1.34, 2.39	1.64	1.23, 2.13	1.08	1.00, 1.62	1.00	N/A
Tumor size, cm3												0.19
≤18	401	1.96	1.51, 3.66	1.96	1.48, 2.97	1.70	1.21, 2.28	1.25	1.00, 1.85	1.00	N/A
>18	391	4.09	1.90, 12.0	1.51	1.17, 2.25	1.23	1.00, 1.64	1.00	1.00, 1.40	1.00	N/A
Duration of phone use, years												0.38
<6	461	2.02	1.31, 4.28	1.39	1.13, 1.99	1.39	1.06, 1.81	1.00	1.00, 1.43	1.00	N/A
≥6	331	3.27	1.92, 11.3	2.32	1.57, 3.57	1.41	1.00, 2.12	1.24	1.00, 1.85	1.00	N/A
Cumulative phone use, hours												0.37
<200	435	1.57	1.29, 3.36	1.57	1.27, 2.22	1.48	1.10, 1.95	1.07	1.00, 1.55	1.00	N/A
≥200	357	4.06	2.03, 11.6	1.94	1.32, 3.02	1.34	1.00, 1.97	1.13	1.00, 1.71	1.00	N/A
Cumulative no. of calls												0.16
<4,000	420	1.55	1.25, 3.42	1.44	1.19, 2.02	1.44	1.10, 1.84	1.00	1.00, 1.37	1.00	N/A
≥4,000	372	3.56	2.05, 9.88	2.26	1.51, 3.38	1.39	1.03, 2.08	1.29	1.00, 1.92	1.00	N/A

Abbreviations: CI, confidence interval; N/A, not applicable.

^a The $\hat{\mathrm{\alpha }}$ values represent the elevation in risk of observing a tumor within a given interval compared with the assumed baseline risk.

^b Side of the head preferred for mobile phone use.

^c Number of tumors within the covariate level.

^d Reference category ($\hat{\mathrm{\alpha }}$ = 1).

^e Test of no difference in distance relationship between levels of the covariate.

^f It was possible to assign tumor grade for only 748 of the 792 regular phone users with information on preferred side of use.