Table 9.

Biological Gradient. Numbers of cases (Ca), controls (Co), and odds ratio (OR) with 95% confidence interval (CI) for cumulative use of mobile phone in hours and glioma risk in Interphone [2].

Cumulative call time (hours)	Ca/Co	OR (95% CI)
Never regular user	1,042/1,078	(1.0)
<5	141/197	0.70 (0.52–0.94)
5–12.9	145/198	0.71 (0.53–0.94)
13–30.9	189/179	1.05 (0.79–1.38)
31–60.9	144/196	0.74 (0.55–0.98)
61–114.9	171/193	0.81 (0.61–1.08)
115–199.9	160/194	0.73 (0.54–0.98)
200–359.9	158/194	0.76 (0.57–1.01)
360–734.9	189/205	0.82 (0.62–1.08)
735–1,639.9	159/184	0.71 (0.53–0.96)
≥1,640	210/154	1.40 (1.03–1.89)
≥1,640∗	160/113	1.82 (1.15–2.89)

^∗Regular use < 5 h = OR 1.0 (ref).