Temporal trends (2016–2023) of undernutrition and anemia among children in poor areas, and relationship between Yingyangbao intervention and children’s nutrition status: a multiwave cross-sectional study in Hunan, China

Yingyangbao is a complementary food supplement provided in Nutrition Improvement Program for Children in Poor Areas (NIPCPA) of China, and is rich in various nutrients, such as proteins, vitamins, and minerals. This study was aimed to describe the temporal trends of undernutrition and anemia among children aged 6–23 months in poor areas in Hunan province from 2016 to 2023, and explore the relationships of Yingyangbao intervention with children’s undernutrition and anemia. Eight rounds of Hunan provincial NIPCPA surveys were conducted using a combination of multi-stage, probability proportionate to size (PPS), and random equidistant sampling of children aged 6–23 months from 2016 to 2023. Multivariate unconditional logistic regressions were fitted to determine the effectiveness of Yingyangbao intervention on children’s undernutrition and anemia. Totally 16,895 children aged 6–23 months were included from 2016 to 2023. The average means of body length, weight, and hemoglobin (Hb) concentration among the children from 2016 to 2023 were 76.8 ± 6.1 cm, 9.95 ± 1.56 kg, and 118.8 ± 11.2 g/L, respectively. The average prevalence of stunting, underweight, wasting, and overall anemia among children from 2016 to 2023 were 4.4%, 3.2%, 3.0%, and 13.6%, respectively. The annual prevalence of stunting declined by 30.9% from 5.5% in 2016 to 3.8% in 2023. The annual prevalence of underweight dropped by 58.0% from 5.0% in 2016 to 2.1% in 2023. The annual prevalence of wasting decreased from 3.8% in 2016 to 1.5% in 2023, with a maximum of 3.8% in both 2016 and 2022. The annual prevalence of overall anemia declined by 78.8% from 29.3% in 2016 to 6.2% in 2023. Logistic regression analysis showed Yingyangbao consumption and duration were both significantly associated with overall anemia and anemia severity, but not with stunting, underweight or wasting. Compared to children without consumption of Yingyangbao, children with effective consumption of Yingyangbao were less likely to have anemia, with adjusted odds ratios (AORs) of 0.43 (95%CI: 0.39–0.49) for mild anemia, 0.20 (0.16–0.26) for moderate anemia, and 0.38 (0.34–0.43) for overall anemia. Compared to children without consumption of Yingyangbao, children with non-effective consumption of Yingyangbao were also less likely to have anemia, with AORs of 0.61 (95%CI: 0.54–0.70) for mild anemia, 0.41 (0.32–0.54) for moderate anemia, and 0.57 (0.50–0.64) for overall anemia. Compared to children without consumption of Yingyangbao (duration for 0 month), children with < 6 months, 6–11 months, and ≥ 12 months of consumption were less likely to have anemia. The AORs were 0.52 (95%CI: 0.43–0.62), 0.50 (0.44–0.56), and 0.46 (0.40–0.54) for mild anemia, respectively; 0.29 (0.23–0.37), 0.24 (0.17–0.34), and 0.21 (0.13–0.33) for moderate anemia, respectively; 0.54 (0.43–0.68), 0.42 (0.36–0.48), and 0.35 (0.27–0.43) for overall anemia, respectively. The prevalence of stunting, underweight and wasting of children aged 6–23 months in poor areas in Hunan are low, while anemia prevalence is a mild public health problem. Yingyangbao intervention can effectively improve the anemia status in children. The effect of effective consumption of Yingyangbao is better than that of non-effective consumption, and a longer duration results in a better improvement effect.