National trends and socioeconomic inequalities in the Composite Index of Severe Anthropometric Failure among children under five in Bangladesh

Severe undernutrition in early childhood remains a major public health challenge in Bangladesh. The Composite Index of Severe Anthropometric Failure (CISAF) provides a more comprehensive metric of undernutrition. The study examined the prevalence, trends, and socioeconomic disparities in CISAF among children under five in Bangladesh using three nationally representative surveys. Data were extracted from the Bangladesh Demographic and Health Survey (BDHS) 2017-18, Multiple Indicator Cluster Survey (MICS) 2019, and BDHS 2022. The study scope was restricted to the most recent survey rounds to reflect current conditions and to maintain consistency with the programme period now used in national planning. Descriptive, regression, and inequality analyses (slope index of inequality [SII], relative index of inequality [RII]) were performed to assess trends and predictors. The Approximate test of homogeneity of odds ratios was used to examine the homogeneity of odds across survey years. Among 33452 children under five, CISAF prevalence significantly declined from 10.3% in 2017-18 to 10.1% in 2019 and finally, 7.6% in 2022. Higher odds of CISAF were observed among older age groups compared with younger groups across all the surveys (aOR: 1.03, 1.10 and 1.02, respectively). However, lower odds were linked to wealthier families and higher education of the mother. SII declined from -0.12 (2017-18) to -0.09 (2022), while RII ranged from 1.41 to 1.54, indicating persistent inequality despite national improvements in severe undernutrition. Severe undernutrition among children under five has declined, but clear socioeconomic gaps remain. Children from poorer households and those with less educated mothers continue to face higher levels of severe anthropometric failure. Equity-focused approaches, including targeted community services, social protection support, and wider access to maternal health information, may help narrow these gaps. Integrating CISAF into routine surveillance could improve identification of high-risk groups and support stronger programme planning.