Vitamin D–Deficient Rickets in Japan

Objectives: Our study aimed to clarify the trend of vitamin D deficiency and rickets diagnosed in the past 10 years. Methods: This observational study used health insurance claims data from 2005 to 2014. The number of beneficiaries for 2005 and 2014 were 91 617 and 365 800, respectively. We included children aged 0 to 15 years diagnosed with vitamin D deficiency or vitamin D–deficient rickets; those with congenital/secondary rickets and low-birth-weight infants were excluded. We analyzed the number of patients and the temporal trend of these diseases in Japan. Results: The annual number of patients from 2005 to 2008 was <5. The number of patients in 2009 and 2014 were 3.88 (95% confidence interval = 1.77-7.37) and 12.30/100 000 (95% confidence interval = 8.97-16.46), respectively. Conclusions: Diagnosed cases of vitamin D deficiency and vitamin D–deficient rickets have apparently increased in Japan. Further studies to identify the trend, cause, and prevention of vitamin D–deficient rickets are necessary.