Epidemiology of Electromagnetic Fields

62 Epidemiology of Electromagnetic Fields

An attempt to reduce the impact of potential selection bias was made by the Interphone

study investigators by restricting the analyses to regular users of mobile phones

(seeAppendix 2 in Interphone Study Group 2010), and using the lowest exposure category

asthe reference category instead of nonregular mobile phone users. This method is based

on theassumption that selection bias from nonparticipation among controls is the only rea-

son for the downward bias of the risk estimates. If this assumption is incorrect, however,

new bias may be introduced and any gain in validity is questionable, because the odds ratios

can be distorted in any direction, and the results will be difcult or impossible to i ...