Increased risk of thyroid cancer among Norwegian women married to fishery workers – a retrospective cohort study

Abstract

Summary The relationship between thyroid cancer in women and the occupation of their spouses was examined in a retrospective cohort study, with special reference to fishery. Of the 2.9 million women registered in the Central Population Registry of Norway on 31 December 1991, 1.2 million women had a spouse registered with an occupation in one or more of the censuses in 1960, 1970 or 1980. The women were assigned to ten broad categories based on the first digit of their husbands five-digit Nordic occupational classification code NYK, and a standardized incidence ratio (SIR) was calculated for each occupational category. The women were further subdivided and analysed in 71 groups defined by the first two digits of the NYK code. Among the women included in the study, a total of 2409 cases of thyroid cancer were reported to the cancer registry of Norway during 1960-92. A significantly elevated risk of thyroid cancer was found only among women whose spouses belonged to the occupational category 'agriculture, forestry or fishery' (n = 208 279), with a SIR of 1.13. In the group associated with 'fishing, whaling and sealing work' (n = 40 839), the risk was further increased (SIR 1.91, Cl 1.65-2.21). An increased risk was also detected in the group associated with 'ship officers and pilots work' (n= 29 133) (SIR 1.35, Cl 1.07-1.67). When allocating the women to southern and northern cohorts determined by their county of birth, a difference in risk was clearly present in all 10 occupational categories, with figures being 50-60% higher in the north. However, there was practically no difference in incidence between northern and southern cohorts among women associated with fishery work. Thus, the results obtained from this study indicate that being a fisherman's wife is associated with elevated risk of thyroid cancer, and our data support the suggested role of seafood as an aetiological factor.

The Norwegian Thyroid Cancer Project: History, achievements and present view on carcinogenesis

“…The risk increases by the number of fish-meals per week. The outcome is compatible with the results published in the study of the thyroid cancer risk of fishermen's wives, published in 1997 (19): In Norway spouses of fishery workers have a higher risk than women married to men of any other main occupational class. The results also suggest that the increased risk is restricted to the older birth cohorts of spouses while younger wives seem to have a risk closer to the population average.…”

Clinico-pathological Features of Thyroid Cancer as Observed in Five Referral Hospitals in Iran

“…In contrast to overall incidence, the distribution of different histologic types of TC differs between IDA and ISA (2,8,23). Several case-control studies have shown that iodine deficiency leads to an increased relative proportion of FTC compared with areas of endemic goiter (12,24) (1996); Harrach and Williams (1995)) have reported a higher incidence of FTC ( 5/30 Á/40%), which may be more prominent in men, in iodine-deficient areas (10, 24 Á/26). Following the introduction of iodine supplementation in iodine-deficient regions, however, an increase in the relative proportion of PTC has been recorded, usually concurrent with a drop in frequency of the follicular and anaplastic types (13,26,27).…”

“…The highest incidence rates are reported in areas of high iodine intake (12); however, there is no general consensus on these findings (13). In fact, the overall incidence of differentiated thyroid carcinoma is not considered to be influenced by iodine intake in a population, whereas the distribution of the types of thyroid carcinoma seems to be related to the intake of iodine, with fewer of the more aggressive follicular and anaplastic carcinomas and more PTC (papillary thyroid carcinomas) being observed in iodine-rich areas.…”

Endocrine cancer in Iran: Based on cancer registry system

“…[22] The result of our study is in accordance with other recent studies on the incidence of thyroid carcinoma in Iran, showing a high rate of papillary carcinoma and a low rate of follicular carcinoma. [18] Previous studies have shown that the most prevalent histology in an endemic goiter region is follicular, [5,23] but if we consider that for ~12 years salt has been iodinized in this region, resulting in a decrease in the prevalence of thyroid goiter, [24] the increase in the incidence of papillary carcinoma can be explained. In addition, previous studies in Iran have shown that even before the salt iodinization process was initiated, papillary carcinoma was the most prevalent histology in Iran.…”