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.