title: Increasing incidence of thyroid cancer in the Nordic countries with main focus on Swedish data.
abstract: Radiofrequency radiation in the frequency range 30 kHz-300 GHz was evaluated to be Group 2B, i.e. 'possibly' carcinogenic to humans, by the International Agency for Research on Cancer (IARC) at WHO in May 2011. Among the evaluated devices were mobile and cordless phones, since they emit radiofrequency electromagnetic fields (RF-EMF). In addition to the brain, another organ, the thyroid gland, also receives high exposure. The incidence of thyroid cancer is increasing in many countries, especially the papillary type that is the most radiosensitive type.
  
  
  
  We used the Swedish Cancer Register to study the incidence of thyroid cancer during 1970-2013 using joinpoint regression analysis.
  
  
  
  In women, the incidence increased statistically significantly during the whole study period; average annual percentage change (AAPC) +1.19 % (95 % confidence interval (CI) +0.56, +1.83 %). Two joinpoints were detected, 1979 and 2001, with a high increase of the incidence during the last period 2001-2013 with an annual percentage change (APC) of +5.34 % (95 % CI +3.93, +6.77 %). AAPC for all men during 1970-2013 was +0.77 % (95 % CI -0.03, +1.58 %). One joinpoint was detected in 2005 with a statistically significant increase in incidence during 2005-2013; APC +7.56 % (95 % CI +3.34, +11.96 %). Based on NORDCAN data, there was a statistically significant increase in the incidence of thyroid cancer in the Nordic countries during the same time period. In both women and men a joinpoint was detected in 2006. The incidence increased during 2006-2013 in women; APC +6.16 % (95 % CI +3.94, +8.42 %) and in men; APC +6.84 % (95 % CI +3.69, +10.08 %), thus showing similar results as the Swedish Cancer Register. Analyses based on data from the Cancer Register showed that the increasing trend in Sweden was mainly caused by thyroid cancer of the papillary type.
  
  
  
  We postulate that the whole increase cannot be attributed to better diagnostic procedures. Increasing exposure to ionizing radiation, e.g. medical computed tomography (CT) scans, and to RF-EMF (non-ionizing radiation) should be further studied. The design of our study does not permit conclusions regarding causality.
authors.affiliation: Department of Oncology, Faculty of Medicine and Health, Örebro University, SE-701 82, Örebro, Sweden. michael.carlberg@regionorebrolan.se.
authors.forename: Michael
authors.initials: M
authors.lastname: Carlberg
authors.affiliation: Independent Environment and Health Research Luleå, Östra Skolgatan 12, SE-972 53, Luleå, Sweden.
authors.forename: Lena
authors.initials: L
authors.lastname: Hedendahl
authors.affiliation: Institute of Environmental Health and Safety, Jaama 14-3, 11615, Tallinn, Estonia.
authors.forename: Mikko
authors.initials: M
authors.lastname: Ahonen
authors.affiliation: Department of Labour Environment and Safety, Tallinn University of Technology, SCO351 Ehitajate tee 5, 19086, Tallinn, Estonia.
authors.forename: Tarmo
authors.initials: T
authors.lastname: Koppel
authors.affiliation: Department of Oncology, Faculty of Medicine and Health, Örebro University, SE-701 82, Örebro, Sweden.
authors.forename: Lennart
authors.initials: L
authors.lastname: Hardell
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D004574:Electromagnetic Fields / Q000009:adverse effects*; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D008875:Middle Aged; D012042:Registries; D012044:Regression Analysis; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology; D013964:Thyroid Neoplasms / Q000453:epidemiology*; D055815:Young Adult
keywords: Cordless phone; Incidence; Ionizing radiation; Mobile phone; NORDCAN; Nordic countries; RF-EMF; Radiofrequency electromagnetic fields; Swedish Cancer Register; Thyroid cancer