Cell phones and intracranial tumors, study 2. A (different) case–

control study on intracranial tumors and cell phone use completed between 1994 and 1998 used a structured questionnaire to explore the relationship between cell phone use and primary brain cancer in 469 cases and 422 controls. Compared with patients who never used handheld cellular telephones, the odds ratio associated with regular use was 0.85 (95% confidence interval 0.6 to 1.2). The OR for infrequent users was 1.0 (0.5 to 2.0). The odds ratio for frequent users was 0.7 (0.3 to 1.4). Odds ratios were less than 1.0 for all histologic categories of brain cancer except for neuroepitheliomatous cancers (odds ratio 2.1; 95% confidence interval 0.9 to 4.7).s Interpret these results in light of the findings from the study described in Exercise 18.13.t