Abstract
This prospective study of 63,090 Norwegian women with 124 cases of thyroid cancer diagnosed during 1961-1989 revealed no strong associations with reproductive factors. Late last birth was related to increased risk, whereas no association was noted with parity. A long reproductive period was related to increased risk of papillary carcinomas, whereas a decreased risk of follicular carcinomas and other adenocarcinomas was observed in women with early menarche and late menopause. The risk of thyroid cancer was significantly increased among women in the occupational category 'fishing, ships officers and crew'. Our results are consistent with a modest effect of certain reproductive factors upon thyroid cancer development.
Highlights
In connection with a screening program for breast cancer in Norway in 1956-1959, detailed data on reproductive factors were collected through personal interviews
The risk of thyroid cancer was highest in the counties of Aust-Agder and Tr0ndelag, whereas no urban/rural gradient was observed
The marked female excess among differentiated thyroid carcinomas indicate that reproductive factors may be of importance for tumour development
Summary
In connection with a screening program for breast cancer in Norway in 1956-1959, detailed data on reproductive factors were collected through personal interviews. The cohort and the methods of follow-up and statistical analysis have previously been described in detail (Kvale et al, 1987). Of 85,063 women aged 32-74 years by 1 January, 1961 in the three counties of Nord-Tr0ndelag, Aust-Agder and Vestfold, 63,090 women attended the screening program and were interviewed. The official registration number served as a unique identification of the record for each women and was used to link follow-up information to our files. Complete information concerning emigrations and deaths was obtained from the Central Bureau of Statistics. Data on cancer registrations, including date of diagnosis and histological type, were supplied by the Cancer Registry of Norway
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