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.
Population, Policy and Practice Programme, UCL Institute of Child Health, London, United Kingdom; and emre.basatemur@ucl.ac.uk.
Emre
E
Basatemur
Research Department of Primary Care and Population Health, University College London, London, United Kingdom.
Laura
L
Horsfall
Research Department of Primary Care and Population Health, University College London, London, United Kingdom.
Louise
L
Marston
Research Department of Primary Care and Population Health, University College London, London, United Kingdom.
Greta
G
Rait
Population, Policy and Practice Programme, UCL Institute of Child Health, London, United Kingdom; and.
Alastair
A
Sutcliffe
D000293:Adolescent; D017677:Age Distribution; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D015999:Multivariate Analysis; D044469:Racial Groups / Q000706:statistics & numerical data; D017678:Sex Distribution; D012923:Social Class; D014808:Vitamin D Deficiency / Q000175:diagnosis / Q000453:epidemiology*