Table 4. Risks of acoustic neuroma in relation to reported side of use of the mobile phone, by laterality of tumour.

	Side of tumour compared with reported side of phone usea
	Ipsilateral			Contralateral
Factor	Cases	Controls	OR (95% CI)	Cases	Controls	OR (95% CI)
Frequency of use
Reference categoryb	457	2444	1.0	446	2497	1.0
Regular use	187	1061	0.9 (0.7–1.1)	198	1008	1.1 (0.9–1.4)
Years since first use
Reference categoryb	457	2444	1.0	446	2497	1.0
1.5–4c	82	557	0.7 (0.5–0.9)d	103	525	1.2 (0.9–1.5)
5–9	74	380	1.0 (0.7–1.3)	75	378	1.1 (0.8–1.5)
⩾10	31	124	1.3 (0.8–2.0)	20	105	1.0 (0.6–1.7)
			P trend=0.4			P trend=0.6
Lifetime years of use
Reference categoryb	457	2444	1.0	446	2497	1.0
0.5–4	111	699	0.8 (0.6–1.0)e	133	654	1.2 (1.0–1.5)
5–9	51	281	0.9 (0.7–1.3)	53	270	1.1 (0.8–1.5)
⩾10	23	72	1.8 (1.1–3.1)e	12	73	0.9 (0.5–1.8)
Not known	2	9	P trend=0.11		11	P trend=0.9
Cumulative hours of use f
Reference categoryb	457	2444	1.0	446	2497	1.0
<median	82	522	0.8 (0.6–1.0)	101	497	1.2 (0.9–1.6)
Median-3rd quartile	41	258	0.8 (0.6–1.2)	49	247	1.2 (0.8–1.6)
>3rd quartile	60	261	1.2 (0.8–1.6)	42	248	0.9 (0.6–1.3)
Not known	4	20	P trend=0.5	6	16	P trend=0.6

^aA total of 29 cases excluded because tumour laterality was not known. Five cases and 11 controls excluded because of lack of phone use data. A total of 37 controls excluded because there were no cases in their matching stratum.

^bThe reference category is never or nonregular use of any type of mobile phone and, in the ipsilateral analysis, phone use only on the opposite side of the tumour, and in the contralateral analysis, phone use only on the same side as the tumour.

^cLower limit 1.5 years ago because regular phone use defined as phone use of at least 6 months’ duration at least 1 year prior to the reference date.

^dP<0.01.

^eP<0.05.

^fClassification based on the distribution among controls who were users. Data were divided into <119, 119–593 and >593 for ipsilateral use, and <122, 122–534 and >534 for contralateral use.