Birth cohort effects underlying the increasing testicular cancer incidence in Canada

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 age-period-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 28 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 bon since 1945; those born between 1959 and 1968 were 2.0 (95% CI, 1.5 26) times as likely to develop testicular cancer has increased over time and changing exposure to environmental factors early in life may be responsible for this.