Symmetry of Age and Sex Distributions in a Cross-sectional Nutrition Survey of Children Under Five in Bolori II, Monguno, and Pulka, Nigeria (2022–2023)

Abstract

Reliable nutrition surveys require representative age and sex distributions to ensure accurate estimation of malnutrition prevalence. This study evaluated the symmetry of age and sex distributions among children aged 6–59 months using data from cross-sectional SMART nutrition surveys conducted in Bolori II, Monguno, and Pulka, Borno State, Nigeria, during 2022–2023. A two-stage cluster sampling technique based on Probability Proportional to Size (PPS) was employed, yielding samples of 785, 592, and 574 children from Bolori II, Monguno, and Pulka, respectively. Age and sex distributions were assessed using frequency distributions, sex ratios, chi-square tests, and anthropometric quality indicators, while Weight-for-Height (WHZ) distributions were compared with the WHO reference standard. The overall male-to-female sex ratios were 1.02, 0.87, and 1.03 for Bolori II, Monguno, and Pulka, respectively, with no statistically significant differences in sex distribution (p = 0.803, 0.100, and 0.738). Mean WHZ values were −0.76 ± 1.05, −1.20 ± 1.18, and −0.57 ± 1.19, indicating poorer nutritional status than the WHO reference, particularly in Monguno. The WHZ distributions exhibited approximately symmetrical bell-shaped patterns with substantial overlap between boys and girls, while design effects ranged from 1.00 to 2.60, confirming acceptable survey quality. Overall, the findings demonstrate that the SMART methodology produced representative and statistically reliable datasets suitable for estimating malnutrition prevalence and supporting evidence-based nutrition interventions in conflict-affected communities.