Regular Article

British Journal of Cancer (2001) 85, 1335–1339. doi:10.1054/bjoc.2001.2061 www.bjcancer.com
Published online 30 October 2001

Increasing thyroid cancer incidence in Canada, 1970–1996: time trends and age-period-cohort effects

S Liu1, R Semenciw2, A-M Ugnat2 and Y Mao2

  1. 1Health Surveillance and Epidemiology Division, Centre for Healthy Human Development, Health Canada, Ottawa
  2. 2Surveillance and Risk Assessment Division, Centre for Chronic Disease Prevention and Control, Health Canada, Ottawa, Canada

Received 9 May 2001; Revised 9 June 2001; Accepted 10 June 2001.

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Abstract

We examined time trends in thyroid cancer incidence in Canada by age, time period and birth cohort between 1970 and 1996. Age-specific incidence rates by time period and birth cohort were calculated and age-period-cohort modelling used to estimate effects underlying the observed trends. Overall age-adjusted incidence rates of thyroid cancer doubled, from 3.3 and 1.1 per 100 000 in 1970–72 to 6.8 and 2.2 per 100 000 in 1994–96, among females and males respectively. Almost all the increase between 1970–72 and 1994–96 was due to papillary carcinoma of the thyroid. Age, birth cohort and period effects significantly improved the fit of the model for females, while age and birth cohort effects were significant determinants of the incidence among males. There were significant differences in the patterns/curvature for age, period and birth cohort effects between women and men. Our results suggest that the increases in thyroid cancer incidence in Canada may be associated with more intensive diagnostic activities and change in radiation exposure in childhood and adolescence. Temporal changes in reproductive factors among young women may explain some of the gender differences observed. © 2001 Cancer Research Campaign www.bjcancer.com

Keywords:

thyroid cancer, incidence, time trends, Poisson regression, Canada

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