Thyroid cancer is a relatively rare cancer (about 3 cases per 100,000 persons per year). The only well-established risk factor is ionizing radiation (e.g., radiotherapy, diagnostic X-ray investigation such as computer tomography, radioactive fallout from atomic weapons and nuclear power plant disasters).
In Sweden, the incidence of thyroid cancer increased during the whole study period 1970 - 2013 in both women and men, although statistically significant only in women. In both genders the incidence significantly increased during the more recent study period, from 2001 in women and from 2005 in men.
In all Nordic countries, a statistically significant increase in the incidence of thyroid cancer was observed during the whole study period 1970 - 2013. The incidence significantly increased from 2006 for both for women and men.
The authors postulate that the whole increase of increase of thyroid cancer cannot be attributed to better diagnostic procedures. Increasing exposure to ionizing radiation (e.g. computed tomography) and to non-ionizing radiofrequency radiation should be further studied.