No child left behind: Policy relevant approaches to measuring and reporting time trends in socio-economic breastfeeding inequalities

Objective: Measuring and monitoring trends in health inequalities is a public health priority. Research has demonstrated that even when overall breastfeeding rates improve, inequality in rates can both persist and worsen. This presentation measures inequality in breastfeeding and illustrates policy-relevant approaches to measuring and assessing trends in inequality. Methods: Data come from the National Immunization Survey, 2005-2011. Outcome variables included “Ever Breastfed,” “Exclusive Breastfeeding at 3 Months,” and “Any Breastfeeding at 6 Months.” Inequality in breastfeeding was measured across income quintiles and racial/ethnic categories. Rate ratios and rate differences compared breastfeeding rates, across groups, at each time point. Concentration curves and indices measured the inequality of breastfeeding across groups, at each time point and provide a visual representation of inequality in breastfeeding. A modified Kakwani index was used to measure the degree that inequalities in breastfeeding reflect underlying socio-economic inequality. Trend analyses and two-sided Z-tests tested for changes, over time. Time by income-quintile and time by racial/ethnic group interactions tested whether breastfeeding rates were statistically significantly different, across groups. Results and Conclusions: Although overall breastfeeding initiation rates may improve, inequalities may persist or worsen. Reporting group-specific rates provides a picture of change across time and may facilitate knowledge translation. Rate ratios may suggest little to no change in inequality while rate differences more accurately reflect changes in disparities over time. Concentration curves and indices provide additional measures of inequality that are visual and easily interpreted. The Kakwani index demonstrates how the US context acts to amplify or mitigate breastfeeding inequalities.