An evaluation of spatio-temporal models for the estimation of the mortality relative risk from breast cancer in Galicia, Spain.

BACKGROUND: Disease mapping is now a big focus of interest in the area of Public Health, and the geographical distribution of a disease has an important role in understanding its origin or its causes. The purpose of this work is to review and evaluate different techniques to map the mortality risk of a disease in small geographical areas. METHODS: Three different methods have been studied. The first one is a classical approach consisting of mapping SMRs, which are maximum likelihood estimates of the relative risk under a Poisson model of death counts. In a second step we consider Poisson and negative binomial regression to fit the rates and finally we use a Bayesian approach that assumes a hierarchical model where the death counts follow a Poisson distribution conditioned by the prior information. These methods have been applied to the study of geographical variation in female breast cancer mortality from 1976 to 1999 in the districts of Galicia, Spain. RESULTS: Mapping the SMRs using the first method has important drawbacks and there are difficulties to distinguish the mortality pattern. With the second method we achieved some improvements. The Bayesian methodology produces smoother maps with a clear mortality pattern. DISCUSSION: These methods are powerful tools for identifying areas with elevated risk. The Bayesian methodology has many advantages over the other methods that had been analysed in this work.

[Space-time distribution of suicide in Galicia, Spain [1976-1998]]. / Distribución geográfica y temporal del suicidio en Galicia (1976-1998).

OBJECTIVE: To study the space-time distribution of suicide in Galicia from 1976 to 1998, taking into account gender, age, season and method of suicide. METHODS: For each sex crude and age-adjusted rates per province and age-specific rates per period (1978-84, 1985-91, 1992-98) were calculated. To estimate mortality risk and time trends in the municipalities, a Bayesian hierarchical model was used. RESULTS: In the last few years mortality from suicide has increase considerably. Age-adjusted rates of 6 per 105 at the beginning of the study rose to 10 per 105 at the end. The increase was greatest among men. The higher rates were observed in the elderly, although in terms of time trends the highest increase occurred among adolescents and young adults. In both sexes the main method of suicide was hanging. Less common methods were jumping from a height and shooting. The greatest number of suicides took place during the spring and summer months. In terms of spatial distribution, a high number of suicides were committed in the province of Lugo; in the municipalities, mortality risk decreased from North to South and an inverse temporal trend was observed in both sexes. This differed from the space-time patterns of suicides committed using methods other than hanging. CONCLUSIONS: Suicide is an important health problem in Galicia not only because to its magnitude but also because of the increasing rates, especially among young people. Geographical and temporal analysis can identify priority areas where preventive policies should be implemented.