Trends in the Diagnosis of Vitamin D Deficiency

BACKGROUND: Vitamin D has attracted considerable interest in recent years, and health care providers have reported large increases in vitamin D test requests. However, rates of diagnosis of vitamin D deficiency in clinical practice have not been investigated. We examined trends in diagnosis of vitamin D deficiency in children in England over time, and by sociodemographic characteristics. METHODS: Cohort study using primary care records of 711 788 children aged 0 to 17 years, from the Health Improvement Network database. Incidence rates for diagnosis of vitamin D deficiency were calculated per year between 2000 and 2014. Rate ratios exploring differences by age, sex, ethnicity, and social deprivation were estimated using multivariable Poisson regression. RESULTS: The crude rate of vitamin D deficiency diagnosis increased from 3.14 per 100 000 person-years in 2000 (95% confidence interval [CI], 1.31-7.54) to 261 per 100 000 person-years in 2014 (95% CI, 241-281). After accounting for changes in demographic characteristics, a 15-fold (95% CI, 10-21) increase in diagnosis was seen between 2008 and 2014. Older age (>= 10 years), nonwhite ethnicity, and social deprivation were independently associated with higher rates of diagnosis. In children aged < 5 years, diagnosis rates were higher in boys than girls, whereas in children aged >= 10 they were higher in girls. CONCLUSIONS: There has been a marked increase in diagnosis of vitamin D deficiency in children over the past decade. Future research should explore the drivers for this change in diagnostic behavior and the reasons prompting investigation of vitamin D status in clinical practice.