Academic journal article Canadian Journal of Public Health

Birth Cohort Effects Underlying the Increasing Testicular Cancer Incidence in Canada

Academic journal article Canadian Journal of Public Health

Birth Cohort Effects Underlying the Increasing Testicular Cancer Incidence in Canada

Article excerpt

ABSTRACT

Purpose: To examine the pattern of testicular cancer incidence by age, time period and birth cohort since 1969 in Canada. Method. In addition to analyses of the secular trends by age group and birth cohort separately, an ageperiod-cohort model and the submodels with standard Poisson assumptions were fitted to the data. Results: The overall age-adjusted incidence of testicular cancer increased in Canada, from 2.8 per 100,000 males in 1969-71 to 4.2 in 1991-93. The younger age groups showed much higher absolute incidence rates in the recent period compared with those in the early period. Age-period-cohort modelling of data restricted to males aged 20-84 years suggested that the observed increase in testicular cancer could be largely attributed to a birth cohort effect. A steady increase in risk was observed among men born since 1945; those born between 1959 and 1968 were 2.0 (95% CI, 1.5 - 2.6) times as likely to develop testicular cancer as those born between 1904 and 1913. Conclusion: The risk of testicular cancer has increased over time and changing exposure to environmental factors early in life may be responsible for this.

ABREGE

Objectif: examiner l'evolution de l'incidence du cancer des testicules par age(overscored), periode de temps et cohorte de naissance depuis 1969 au Canada. Methode: outre les analyses de tendances generales par categorie d'age(overscored) et cohorte de nuissance separement, on a applique aux donnees un modele age(overscored)-periode-cohorte et les sous-modeles avec les hypotheses habituelles de Poisson. Resultats: l'incidence generale, ajustee selon l'age, du cancer des testicules a augmente au Canada, passant de 2,8 pour 100 000 hommes en 1969-1971 a 4,2 en 1991-1993. Les categories d'age(overscored) plus jeune sont apparues avoir des taux d'incidence absolus beaucoup plus eleves au cours de la periode recente en comparaison avec la periode anterieure. La modelisation age(overscored)-periode de temps-cohorte des donnees limitee aux hommes ages(overscored) de 20 a 84 ans suggere que l'augmentation constatee du cancer des testicules pourrait etre largement attribuable a un effet de cohorte de naissance. On a observe une augmentation reguliere du risque chez les hommes nes apres 1945; les individus nes entre 1959 et 1968 avaient 2,0 (95% IC, 1.5 - 2.6) plus de probabilite de developper un cancer des testicules que ceux nes entre 1904 et 1913. Conclusion: le risque de cancer des testicules a augmente et les changements de l'exposition auz facteurs environnementaux au debut de la vie pouraient en etre la cause.

Testicular cancer is a relatively rare disease, accounting for only 1.1% of all malignant neoplasms in men, but it is the most common cancer in young and middle-aged males. More importantly, the age-adjusted incidence rate has been increasing by 1.6% per year between 1985 and 1992 in Canadian men.1 Studies from other countries have also shown a dramatic increase in the incidence of testicular cancer during the past several decades.2 The age-standardized incidence rate has doubled every 15 to 25 years in Northern European countries,7 and the increasing trend in testicular cancer risk has been shown to follow a birth cohort pattern.2 A recent study showed that the ageadjusted incidence rate of testicular cancer has increased 3.5-fold in Connecticut, USA during the last 60 years of cancer registration.3 The cause of these trends is unknown.

Most of the previous studies have been carried out in European countries and the United States. No comparable analysis of testicular cancer trends has been reported from Canada. The purpose of the current study was to examine the pattern of testicular cancer incidence by age, time period and birth cohort in Canada.

METHODS

Data source

Data on the incidence of testicular cancer were obtained from the National Cancer Incidence Reporting System (NCIRS) of Statistics Canada, which began collecting data from provincial and territorial cancer registries in 1969. …

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