Brain cancer mortality in an agricultural and a metropolitan region of Rio de Janeiro, Brazil: a population-based, age-period-cohort study, 1996-2010

Abstract

Background: Individuals who live in rural areas are at greater risk for brain cancer, and pesticide exposure may contribute to this increased risk. The aims of this research were to analyze the mortality trends and to estimate the age-period-cohort effects on mortality rates from brain cancer in two regions in Rio de Janeiro, Brazil.

Methods: This descriptive study examined brain cancer mortality patterns in individuals of both sexes, >19 years of age, who died between 1996 and 2010. They were residents of a rural (Serrana) or a non-rural (Metropolitan) area of Rio de Janeiro, Brazil. We estimated mortality trends using Joinpoint Regression analysis. Age-period-cohort models were estimated using Poisson regression analysis.

Results: The estimated annual percentage change in mortality caused by brain cancer was 3.8% in the Serrana Region (95% confidence interval (CI): 0.8-5.6) and -0.2% (95% CI: -1.2-0.7) in the Metropolitan Region. The results indicated that the relative risk was higher in the rural region for the more recent birth cohorts (1954 and later). Compared with the reference birth cohort (1945-49, Serrana Region), the relative risk was four times higher for individuals born between 1985 and 1989.

Conclusions: The results of this study indicate that there is an increasing trend in brain cancer mortality rates in the rural Serrana Region in Brazil. A cohort effect occurred in the birth cohorts born in this rural area after 1954. At the ecological level, different environmental factors, especially the use of pesticides, may explain regional disparities in the mortality patterns from brain cancers.

Figure 1

Trends in mortality from brain cancer adjusted by world standard population in the Serrana region and Metropolitan area of Rio de Janeiro between 1996 and 2010. Axis Y shows the mortality rates per one hundred thousand inhabitants and axis X shows the calendar year.

Figure 2

Estimates of the age-period-cohort effects on brain cancer mortality in residents of the Serrana and Metropolitan regions of the state of Rio de Janeiro, 20 to 79 years of age, from 1996 to 2010: The figures shows: Right – brain cancer mortality rates to 100 thousand inhabitants; Center - brain cancer mortality effects by birth cohort. Left – effects by death period.

Figure 3

Comparing age-period-cohort of age-specific mortality rate. Axis X shows the effect of Age-period-cohort and axis Y shows the (log) mortality rates per one hundred thousand inhabitants.