The effect of redistribution of ill-defined causes of death on the mortality rate of breast cancer in Brazil.

The relevance of breast cancer for women has driven research about mortality of this disease. However, these studies are affected by problems generated by deaths due to ill-defined causes (IDC). To highlight distortions caused by IDC in studies that evaluate mortality, we calculated the age-standardized mortality rates of breast cancer, with and without adjustment for IDC for the years 1990, 2000, and 2010. Then, panel data regression models were estimated and enabled us to identify that the adjustment for IDC: has elevated breast cancer mortality rate of Brazilian municipalities by 9% in the period considered; has drawn mortality rates of the South, Southeast, Northeast and North regions closer; has reduced the increasing trend of mortality by almost 60%, mainly in the Southeast and South regions; has increased, more sharply, the mortality in cities with less than 5 thousand inhabitants; has curbed the significance of most factors associated with breast cancer; has revealed that the effect of longevity and the public health expenditure may be overestimated. These results highlight the importance of adjustment for IDC in producing reliable mortality indicators.