Effect of a School-Based Physical Activity and Multi-Micronutrient Supplementation Intervention on Cognitive Function and Academic Achievement Among Schoolchildren in Tanzania: Secondary Outcome from the KaziAfya Cluster-Randomized Controlled Trial

Background: Physical activity (PA) and adequate micronutrient intake are essential for brain development and may influence cognitive function and academic achievement. However, few large-scale studies have assessed the combined effects of PA and multi-micronutrient supplementation (MMNS) in school-age children. Methods: A cluster-randomized placebo-controlled trial in four peri-urban Tanzanian schools assigned children to one of four groups: (i) PA alone; (ii) MMNS alone; (iii) PA plus MMNS; or (iv) placebo. Children were followed over two school years with assessments at baseline, 14 months, and 26 months. Cognitive function was assessed using computerized Flanker tasks. Academic achievement was evaluated through end-of-year exams in mathematics and Kiswahili subject scores. Anthropometric measures determined nutritional status. Data were analyzed using generalized estimated equations (GEE). Results: Complete data from 559 children (326 girls, 233 boys) aged 6–12 years showed differing characteristics across groups, particularly age and body mass index. No significant intervention effects on cognitive function were found. MMNS groups (alone or combined with PA) showed significantly higher Kiswahili scores, while PA alone had the lowest performance compared to placebo. No intervention effect was found in mathematics. Sex, hemoglobin level, and baseline measures were key predictors for cognition or academic performance. Conclusions: PA and MMNS interventions showed no significant cognitive or academic improvements versus placebo. Further research should optimize school-based nutrition and PA programs for improved learning outcomes.