Incidence and clinical characteristics of pediatric vitamin D deficiency in Hokkaido, Japan: A survey of cases diagnosed between 2015 and 2019

Vitamin D deficiency and rickets are important pediatric health concerns, particularly in high-latitude regions. This study investigated the incidence and clinical characteristics of pediatric vitamin D deficiency in Hokkaido, Japan, between 2015 and 2019. A cross-sectional survey was distributed to the pediatric departments of 88 major hospitals across the region, achieving a response rate of 97.7%. Clinical data were collected from 262 children with vitamin D deficiency (25(OH)D < 20 ng/mL), including 153 with rickets. In 2019, the incidence of vitamin D deficiency rickets was 25.4 per 100,000 live births, approximately threefold higher than 15 yr earlier and eightfold greater than the national average. Most cases (median age 1.4–1.5 yr) occurred in children younger than four years. Patients with rickets exhibited considerably lower Ca/P and higher ALP/iPTH levels than those without rickets, despite having similar 25(OH)D levels. Exclusive breastfeeding was significantly more common in the rickets group. Approximately 90% of patients received alfacalcidol. The incidence of pediatric vitamin D deficiency and rickets in Hokkaido has increased. These findings underscore the need for continued public health education on vitamin D intake, expanded access to native vitamin D supplementation, and attention to maternal vitamin D status.