The geography of the highest mortality areas in Spain: a striking cluster in the southwestern region of the country.

AIMS To determine the areas of Spain with the most increased mortality risk. METHODS Age adjusted relative risk of death by gender was estimated in each of 2218 small areas of the country using a non-parametric empirical Bayes method. To determine areas with "significantly increased risk" a Poisson based score test was used. RESULTS Mapping of the highest risk areas showed a striking geographical clustering in the southwestern region of the country. This region, comprising 8% of the Spanish population, accounts for about one third (2884 deaths) of the total excess mortality.