IS RESIDENCE IN AREAS OF ENDEMIC GOITER A RISK FACTOR FOR THYROID-CANCER

The association between an indicator of iodine deficiency and differen tiated thyroid cancer has been investigated in a population-based case -control study. This included all incident cases (N = 484) of papillar y and follicular thyroid cancer diagnosed during the years 1980-1992 i n a Swedish Health Care Region among residents born in Sweden, and as many individually matched controls. Cases were included after a unifor m review of their histopathological specimens. Residence in areas wher e goiter had been severely endemic in the 1930s was used as exposure i ndicator. Odds ratios (OR) and 95% confidence intervals as estimates o f relative risk were calculated as a measure of association using logi stic regression. A trend toward an association was found with a durati on of residence in goiter areas between 21 and 40 years, most prominen t among follicular cancer cases and in the group diagnosed at age grea ter than or equal to 50 years compared to not exposed. Exposure for th e first time during adolescence (between 11 and 20 years) was associat ed with an increased risk of papillary cancer. This was especially evi dent among women, both when compared to not exposed and to those expos ed during the first year of life; the association was strengthened aft er adjustment for duration of residence. These findings support the hy pothesis of distinct causation patterns from iodine deficiency to the 2 most common histological types of thyroid cancer. (C) 1995 Utilty-Li ss, Inc.