Cellular telephones and cancer - A nationwide cohort study in Denmark

Background: Use of cellular telephones is increasing exponentially and has become part of everyday life. Concerns about possible carcinogenic effects of radiofrequency signals have been raised, although they are based on limi ted scientific evidence. Methods: A retrospective cohort study of cancer in cidence was conducted in Denmark of all users of cellular telephones during the period from 1982 through 1995, Subscriber lists from the two Danish op erating companies identified 420095 cellular telephone users. Cancer incide nce was determined by linkage with the Danish Cancer Registry. All statisti cal tests are two-sided. Results: Overall, 3391 cancers were observed with 3825 expected, yielding a significantly decreased standardized incidence ra tio (SIR) of 0.89 (95% confidence interval [CI] = 0.86 to 0.92), A substant ial proportion of this decreased risk was attributed to deficits of lung ca ncer and other smoking-related cancers. No excesses were observed for cance rs of the brain or nervous system (SIR = 0.95; 95% CI = 0.81 to 1.12) or of the salivary gland (SIR = 0.72; 95% CI = 0.29 to 1.49) or for leukemia (SI R = 0.97; 95% CI = 0.78-1.21), cancers of a priori interest. Risk for these cancers also did not vary by duration of cellular telephone use, time sinc e first subscription, age at first subscription, or type of cellular teleph one (analogue or digital). Analysis of brain and nervous system tumors show ed no statistically significant SIRs for any subtype or anatomic location. Conclusions: The results of this investigation, the first nationwide cancer incidence study of cellular phone users, do not support the hypothesis of an association between use of these telephones and tumors of the brain or s alivary gland, leukemia, or other cancers.