Background and objective: Time trend of breast cancer incidence in Catalonia in the last 20 years is evaluated by a age-period-cohort model.
Population and method: Women older than 25 years diagnosed with breast cancer between 1980 and 1999 in the population covered by Tarragona and Girona population-based cancer registries. To investigate the age, period and birth cohort effect in the time trends of breast cancer incidence, Decarli and La Vecchia and Holdford's methods were used.
Results: The world age-standardized rate (25 to > or = 85 years old) has increased from 53.9 cases per 100,000 women-year in the period 1980-1984 to 83.9 per 100,000 women-year in the period 1995-1999. The annual percentage change was 2.2% (95% confidence interval, 1.8-2.6). According to age-period-cohort model an increment of the incidence exists depending on age and birth cohort, being the period effect less important.
Conclusions: Breast cancer incidence has significantly increased in Catalonia. The birth cohort seems to be more important than the period effect in this increment, which supposes a change on the prevalence of the risk factor, although the use of screening diagnosis techniques might explain a part of the period effect.