Premium
Thyroid cancer in Denmark 1943–2008, before and after iodine supplementation
Author(s) -
Blomberg M.,
FeldtRasmussen U.,
Andersen K.K.,
Kjaer S.K.
Publication year - 2012
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.27497
Subject(s) - thyroid cancer , medicine , incidence (geometry) , cancer registry , cancer , demography , poisson regression , cohort , papillary thyroid cancer , thyroid , pediatrics , population , environmental health , physics , sociology , optics
Thyroid cancer incidence has increased worldwide during the previous decades. In this nationwide study, we aimed to identify the overall incidence of thyroid cancer in Denmark during 66 years (1943–2008) and incidences of the four main histological types of thyroid cancer from 1978 to 2008. Data were obtained from the nationwide Danish Cancer Registry, and we focused especially on the period after implementation of compulsory iodine supplementation, which was established on a national level in 2000. We calculated age‐standardized incidence rates per 100,000 person‐years, and age‐period‐cohort models were fitted to describe trends in incidence. To quantify trends in incidence over time, log‐linear Poisson models were used to estimate annual percentage change. From 1943 to 2008, 1,947 men (29%) and 4,682 women (71%) were diagnosed with thyroid cancer. The age‐standardized incidence increased in both sexes; in men from 0.41 to 1.57 per 100,000 and from 0.90 to 4.11 per 100,000 in women, corresponding to a significant average annual percentage change of 1.7 and 1.8%, respectively. The incidence increased with younger birth cohorts. The rise was almost exclusively caused by papillary carcinomas, and it was particularly present during the last decades of the study period. It cannot be ruled out that iodine supplementation may play a role for the risk of thyroid cancer, but as the strongest increase in incidence began in the years before the implementation, it is likely that improvement in diagnostic modalities increased diagnostic activity, and/or new unknown risk factors are also important contributors to the increase.