Trend and determinants of underweight among children aged under five years in Rwanda: secondary data analysis using Rwanda Demographic Health Surveys 2005–2020

Underweight remains a significant public health concern among children under five years, particularly in low- and middle-income countries. Globally, 149 million are stunted, 45million are wasted, while 37 million are overweight. This study aimed to assess the trends and determinants of underweight among children under five years in Rwanda using nationally representative data from 2005 to 2020. A pooled data analysis of four consecutive Rwanda Demographic and Health Surveys (RDHS) conducted in 2005, 2010, 2015 and 2019/20 was performed. A total of 15,561 children under five years were included in the analysis. Descriptive statistics, bivariate, and multivariable analyses using logistic regression were performed. Sample weights were applied so that the sample accurately represents the whole population. The prevalence of underweight declined substantially from 21.7% in 2005 to 11.4% in 2010, 9.1% in 2015, and 7.7% in 2020, representing a 64% relative reduction over 15 years. In multivariable analysis, male sex (AOR = 3.11, 95% CI 1.97-4.91), very small birth size (AOR = 6.29, 95% CI 1.75-22.60), smaller than average birth size (AOR = 2.66, 95% CI 1.54-4.60), low birth weight < 2.5 kg (AOR = 2.49, 95% CI 1.08-5.69), lack of antenatal care (AOR = 3.99, 95% CI 1.20-13.25), recent diarrhea (AOR = 1.75, 95% CI 1.06-2.90), and Muslim religion (AOR = 4.94, 95% CI 1.39-17.54) remained independently associated with underweight. Mothers aged 20-24 years (AOR = 0.29, 95% CI 0.12-0.69), 25-29 years (AOR = 0.41, 95% CI 0.19-0.89) and 35-39 years (AOR = 0.38, 95% CI 0.18-0.79) showed protective effects compared to mothers aged 40 years and above. Rwanda has achieved remarkable and sustained progress in reducing underweight among children aged under five years over the past 15 years, attributable to improvements in maternal health services, nutrition programs, and broader socioeconomic development. Nonetheless, underweight remains a public health concern, particularly among male children, those born small or with low birth weight, children exposed to recent illness, and those whose mothers lack adequate antenatal care. Sustained multi-sectoral efforts to strengthen antenatal care, reduce low birth weight, and address childhood illness are essential to maintaining and accelerating these gains toward the Sustainable Development Goals (SDGs) targets.