Frequency of suspected anemia in Japanese children aged 1–5 years using noninvasive hemoglobin measurement and influence of iron-fortified growing-up formula intake

Early childhood anemia can impair growth and neurodevelopment. Although noninvasive hemoglobin (SpHb) measurement is a promising alternative to blood sampling, its large-scale use in pediatric populations remains limited. This observational study estimated the frequency of suspected anemia in Japanese children aged 1–5 years and examined the association between Growing-up Formula (GuF) intake and SpHb in the highest-use age band (12–23 months). Overall, 13,642 children were recruited from November 2022 to August 2024. Hb levels were noninvasively measured using the Masimo Rad-67 device. Suspected anemia was defined as an SpHb level < 11.0 g/dL for children aged 12–59 months and < 11.5 g/dL for those aged 60–71 months. Multiple regression analysis in the 12–23-month subgroup was performed to evaluate the association between SpHb levels and GuF intake, after adjusting for age, sex, birth weight, and school lunch consumption. Of the 12,714 eligible children aged 1–5 years, 4.1% were identified as having suspected anemia (range: 2.3%–6.6% across subgroups). In a subgroup of 2,500 children aged 12–23 months, the age group with the highest GuF use in the study population, GuF intake volume was positively associated with SpHb levels ( p = 0.02, R² = 0.012). This study describes the frequency of suspected anemia among Japanese children aged 1–5 years (4.1%) and shows that higher daily GuF intake was associated with higher SpHb levels in children aged 12–23 months, although GuF intake explained only a small proportion of the variance in SpHb levels.