Prevalence and factors related to hypouricemia and hyperuricemia in schoolchildren: results of a large-scale cross-sectional population-based study conducted in Japan

Hypouricemia in children including renal hypouricemia, which is a major cause of exercise-induced acute renal injury (EIAKI), is an important clinical problem, in addition to hyperuricemia. However, no large-scale studies of serum uric acid (UA) concentrations in the general pre-adolescent population have been carried out. We conducted a population-based cross-sectional study to measure the prevalences of hypouricemia and hyperuricemia and identify the associated factors. We analyzed 31,822 (16,205 boys and 15,617 girls) 9–10-year-old children who underwent pediatric health check-ups in Kagawa prefecture between 2014 and 2018. Hypouricemia and hyperuricemia were defined using serum UA concentrations of ≤ 2.0 mg/dL and ≥ 6.0 mg/dL, respectively. The prevalence of hypouricemia was 0.38% in both 9- and 10-year-old boys and girls, and was not significantly associated with age, sex, or environmental factors, including overweight. The prevalence of hyperuricemia was significantly higher in boys (2.7%) than in girls (1.9%), and was significantly associated with age, overweight, future diabetes risk, hypertriglyceridemia, low high-density lipoprotein-cholesterol, and liver damage, but not with high low-density lipoprotein cholesterol. Therefore, some pre-adolescent children in the general population in Japan showed hypouricemia. A means of identifying children with hypouricemia and lifestyle guidance measures for the prevention of EIAKI should be established.