Brain cancer incidence in the provinces of Zaragoza and Navarre (Spain): effect of age, period and birth cohort

Several studies have detected increases in malignant brain tumour incidence and mortality rates particularly among the elderly. We analyzed time trend s in malignant brain tumors incidence in Zaragoza over the period 1973-1990 and Navarre over the period 1973-1991, two Spanish provinces that have bee n collecting data through their respective Cancer Registries for the last 2 0 years, using Poisson regression analysis of age, period of diagnosis and cohort. In general, age-adjusted rates showed a steady rise in both registr ies, except in the case of females in Navarre, for whom a decrease in risk was observed for the last period, 1988-1991. This increase is a reflection of the rise in incidence experienced by the elderly, since the cohorts succ essively register rates that are stable over time, and even downward in the case of females in Navarre. The risk run by generations born circa 1920-19 30 was the highest encountered. Rates were higher in Navarre in both sexes and for all but the last period in females, when rates on the two registers stood level. Increasingly generalised use of CT scanning and magnetic reso nance in the 1980s in Spain, coupled with better and more effective health carl access for the elderly, are factors that may well have some bearing on these findings. (C) 1999 Elsevier Science B.V. All rights reserved.