Birth cohort effects underlying the increasing testicular cancer incidence in Canada.
OBJECTIVE
To examine the pattern of testicular cancer incidence by age, time period and birth cohort since 1969 in Canada.


METHODS
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 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.


CONCLUSIONS
The risk of testicular cancer has increased over time and changing exposure to environmental factors early in life may be responsible for this.
Bureau of Reproductive and Child Health, Laboratory Centre for Disease Control, Ottawa, ON. shiliang_liu@hc-sc.gc.ca
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Liu
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Wen
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Mao
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Mery
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Rouleau
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002170:Canada / Q000453:epidemiology; D015331:Cohort Studies; D004781:Environmental Exposure / Q000009:adverse effects; D006801:Humans; D015994:Incidence; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D012307:Risk Factors; D013736:Testicular Neoplasms / Q000453:epidemiology* / Q000209:etiology