Evaluation of Mobile Phone and Cordless Phone Use and Glioma Risk Using the Bradford Hill Viewpoints from 1965 on Association or Causation
Table 11
Biological Gradient. Numbers of cases (Ca), controls (Co), and odds ratio (OR) with 95% confidence interval (CI) for cumulative duration of calls (hours) of wireless phones in quartiles in Hardell and Carlberg [38].
Quartile
Mobile phone
Cordless phone
Wireless phone
OR, CI (Ca/Co)
OR, CI (Ca/Co)
OR, CI (Ca/Co)
First quartile, all
1.27 1.05–1.54 (340/920)
1.09 0.86–1.39 (174/478)
1.15 0.94–1.42 (223/641)
Second quartile, all
1.29 1.02–1.65 (198/492)
1.23 0.97–1.57 (203/534)
1.29 1.04–1.61 (235/596)
Third quartile, all
1.36 1.04–1.78 (179/416)
1.64 1.28–2.11 (210/451)
1.37 1.08–1.72 (249/617)
Fourth quartile, all
2.22 1.68–2.92 (228/320)
2.35 1.78–3.10 (165/261)
2.04 1.61–2.57 (367/618)
, trend
<0.0001
<0.0001
<0.0001
First quartile 1–122 h; second quartile 123–511 h; third quartile 512–1,486 h; fourth quartile > 1,486 h.