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 and NORDCAN to study the incidence of thyroid cancer during 1970-2013 using joinpoint regression analysis. The incidence increased during the whole study period in both men and women. 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 one joinpoint was detected in 2006. The incidence increased substantially during 2006-2013 in women; annual percentage change (APC) +6.16 % (95 % CI +3.94, +8.42 %) and in men; APC +6.84 % (95 % CI +3.69, +10.08 %). These results were similar as in 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 CT scans, and to radiofrequency radiation (non-ionizing radiation) should be further studied as causative factors to this emerging thyroid cancer health problem.
One aspect to be studied is the increasing use of mobile phones. The antenna was previously placed at the top of the phone but is usually now placed at the bottom in smartphones. This gives higher exposure of radiofrequency radiation to the thyroid gland, see figure. A smartphone can in addition have multiple antennas.