Major reduction in AIDS-mortality inequalities after HAART: The importance of absolute differences in evaluating interventions

This study estimates the magnitude of inequalities in AIDS mortality in the period when highly active antiretroviral therapy (HAART) was introduced and after its widespread dissemination in the Region of Madrid, Spain. Two population cohorts were constructed by linking records from 1996 and 2001 population censuses with mortality registry records after initial and full implementation of HAART, respectively. Absolute and relative differences in AIDS mortality in people aged 20-49 years were estimated in each population cohort according to neighbourhood and individual socioeconomic position. The absolute difference in mortality between neighbourhoods with highest and lowest socioeconomic position (unemployment rate, per capita income) declined from about 30/100,000 person-years in the 1996 population cohort to 8/100,000 person-years in the 2001 population cohort. The absolute difference in mortality between individuals with the highest and lowest socioeconomic position fell from about 60/100,000 person-years in the first cohort to about 20/100,000 in the second. Relative differences in mortality by neighbourhood socioeconomic position and by individual education level also decreased in the 2001 cohort with respect to the 1996 cohort. Although relative differences by individual occupation increased, there was no evidence of a significant change. These findings show major reduction in absolute socioeconomic differences in AIDS mortality after HAART and indicate that the use of relative differences alone may be inadequate to fully evaluate the results of health interventions.