Geographic variation of secular trends of breast cancer mortality in Spain.

Breast cancer mortality information contained in the available statistics derived from the Spanish death certificates has been reviewed. Mortality from breast neoplasms was grouped into three five-year periods: 1903-1907, 1931-1935 and 1975-1979. Age-adjusted rates were estimated for every province (n = 49) in each period, and confidence intervals for the standardized mortality ratios and adjusted rates were calculated. Results are presented with maps of Spain that illustrate provincial contrasts in each period. Secular breast cancer mortality trends in the provinces are discussed in comparison with those of other countries. Furthermore, values are compared with the geographical distribution of risk factors, the aim being to formulate hypothesis explaining the observed contrasts and suggesting some future research lines.