title: Mobile phone use and incidence of glioma in the Nordic countries 1979-2008: consistency check.
abstract: BACKGROUND
  Some case-control studies have reported increased risks of glioma associated with mobile phone use. If true, this would ultimately affect the time trends for incidence rates (IRs). Correspondingly, lack of change in IRs would exclude certain magnitudes of risk. We investigated glioma IR trends in the Nordic countries, and compared the observed with expected incidence rates under various risk scenarios.
  
  
  METHODS
  We analyzed annual age-standardized incidence rates in men and women aged 20 to 79 years during 1979-2008 using joinpoint regression (35,250 glioma cases). Probabilities of detecting various levels of relative risk were computed using simulations.
  
  
  RESULTS
  For the period 1979 through 2008, the annual percent change in incidence rates was 0.4% (95% confidence interval = 0.1% to 0.6%) among men and 0.3% (0.1% to 0.5%) among women. Incidence rates have decreased in young men (20-39 years) since 1987, remained stable in middle-aged men (40-59 years) throughout the 30-year study period, and increased slightly in older men (60-79 years). In simulations, assumed relative risks for all users of 2.0 for an induction time of up to 15 years, 1.5 for up to 10 years, and 1.2 for up to 5 years were incompatible with observed incidence time trends. For heavy users of mobile phones, risks of 2.0 for up to 5 years' induction were also incompatible.
  
  
  CONCLUSIONS
  No clear trend change in glioma incidence rates was observed. Several of the risk increases seen in case-control studies appear to be incompatible with the observed lack of incidence rate increase in middle-aged men. This suggests longer induction periods than currently investigated, lower risks than reported from some case-control studies, or the absence of any association.
authors.affiliation: Section of Environment and Radiation, International Agency for Research on Cancer, Lyon, France. deltouri@iarc.fr
authors.forename: Isabelle
authors.initials: I
authors.lastname: Deltour
authors.forename: Anssi
authors.initials: A
authors.lastname: Auvinen
authors.forename: Maria
authors.initials: M
authors.lastname: Feychting
authors.forename: Christoffer
authors.initials: C
authors.lastname: Johansen
authors.forename: Lars
authors.initials: L
authors.lastname: Klaeboe
authors.forename: Risto
authors.initials: R
authors.lastname: Sankila
authors.forename: Joachim
authors.initials: J
authors.lastname: Schüz
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001932:Brain Neoplasms / Q000453:epidemiology* / Q000209:etiology; D040421:Cell Phone / Q000706:statistics & numerical data; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005387:Finland / Q000453:epidemiology; D005910:Glioma / Q000453:epidemiology* / Q000209:etiology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D012307:Risk Factors; D012737:Sex Factors; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult