Trends in infant mortality inequalities in the Americas: 1955-1995.

STUDY
OBJECTIVE: s: To describe overall and income related trends in infant mortality inequalities in the Region of the Americas from 1955 to 1995.
DESIGN: Infant mortality rates (IMRs) were computed and their trends assessed by ordinary least squares. Overall trends in IMR inequalities among countries were analysed by comparing 10 year period IMRs, Gini coefficients, and Lorenz curves. Income related trends in IMR inequalities were assessed using 10 year period IMR ratios between the highest and the lowest quintiles of the per capita gross national product (GNP) distributions (adjusted for purchasing power).
SETTING: Aggregated country data were used for all countries with over 200 thousand inhabitants (33 geopolitical units). The 10 year period midpoint IMR estimates used for the 1955-1995 time series were those published by the United Nations in 1997. MAIN
RESULTS: IMRs decreased from 90.34 to 31.31 per 1000 live births between 1955 and 1995 at an average of 15.3 every 10 years. In contrast, Lorenz curves and Gini coefficients were similar for the five 10 year periods. After grouping by adjusted GNP distribution, a similar decreasing trend of IMR was observed in all groups. The rate ratio between the group at the lowest quintile and that at the highest quintile ranged from 4 to 5. The analysis of variance for repeated observations showed that there is a significant reduction in the IMR (F=130.18; p<0.01), that trends did not differ significantly among groups (F=1.16; p=0.32), and that they were approximately linear (F=155.83; p<0.01).
CONCLUSIONS: Despite a sizable reduction in the infant mortality, whether or not income related, levels of IMR inequality among countries have remained almost constant between 1955 and 1995 in the Region of the Americas. Further analysis and focused interventions are needed to tackle the challenges of reducing these persistent mortality inequalities.