High prevalence of vitamin D deficiency among school-age children in Tunisia: a first national cross-sectional study.

Globally, vitamin D deficiency (VDD) represents a significant public health concern. Population-level data on vitamin D status in Tunisia are lacking. This study aimed to estimate the national prevalence of VDD among Tunisian school-aged children and identify associated factors. A national cross-sectional survey in 2023 randomly sampled 2670 children aged 6-12 years. Plasma 25-hydroxyvitamin D was measured. Dietary vitamin D (VD) intake and socio-demographics were assessed via questionnaires. Logistic regression identified factors associated to inadequate VD status. The prevalence of VDD (< 30 nmol/L) was 15.8%. Adjusted analysis showed that older children (10-12 years) had a 1.4-fold (P = 0.030) higher likelihood of VDD than younger children. Girls were twice as likely to be VD deficient as boys (adjusted relative prevalence ratio (aRPR) = 2.1; P = 0.001). Significant regional variations in VDD were observed (P < 0.0001). Low and moderate consumption of VD-rich foods was associated with significantly increased odds of severe deficiency (aRRR = 2.0, P = 0.026; aRRR = 1.6, P = 0.005, respectively) relative to high consumption. Finally, overweight status was associated with a 2.0-fold (P < 0.0001) increased odds of severe VDD compared to children with normal weight. VDD is prevalent and increases with age. Vitamin D supplementation strategies should be considered to optimize vitamin D status among children.