The Complexity of the Seasonality of Nutritional Status: Two Annul Peaks in Child Wasting in Eastern Chad.

This article focuses on identifying intra-year variability in childhood wasting, severe wasting, and weight-for-height z-scores (WHZ) in eastern Chad, a dryland region with a single wet season, using data from a 23-month panel study of 231 children aged 6 to 59 months. The analysis, employing mixed-effects harmonic regression, reveals two distinct annual peaks of wasting: a primary peak around mid-May coinciding with high temperatures and the onset of rains, and a secondary peak near October/November at the end of the rainy season. Temperature, rather than rainfall, is significantly associated with increased odds of wasting and severe wasting. These findings challenge the common assumption that wasting peaks only during the "lean" or rainy season and suggest multiple seasonal drivers—including food insecurity, infectious disease, water contamination, and care practices—varying throughout the year. The study underscores the importance of nuanced, high-frequency seasonality analysis to better time and tailor nutrition interventions and improve monitoring of progress toward global nutrition goals.