Kids' Vitamin D Prescriptions Soar in UK

Laird Harrison

December 10, 2019

Doctors in the United Kingdom have dramatically increased their vitamin D prescriptions for children, despite conflicting evidence of benefits.

The number of new prescriptions soared 26-fold between 2008 and 2016, Mandy Wan, MPharm, MSc, of Guy's and Saint Thomas' NHS Foundation Trust, London, UK, and colleagues report in an article published online December 3 in BMJ Open.

Many children received prescriptions at larger doses than recommended by UK guidelines. "This aberrant prescribing practice incurs a huge, potentially avoidable, expense to our healthcare system," the authors warn.

Research has linked vitamin D deficiency to a plethora of health problems, including rickets, hypocalcemic seizures, asthma, eczema, respiratory tract infections, and diabetes.

Vitamin D deficiency is "widely prevalent and seen as a growing public health concern worldwide," the researchers write, with laboratory testing on the rise.

But the majority of randomized trials "do not show improved outcomes with vitamin D supplementation, and meta-analyses are inconclusive and widely debated," Wan and colleagues write.

Government guidelines in the UK call for supplements for children younger than 5 years and for any children whose 25(OH)D concentration is below 25 nmol/L, the threshold set by the UK Scientific Advisory Committee on Nutrition as vitamin D deficient.

To see how these guidelines have translated to practice, the researchers analyzed electronic medical records from UK general practices contributing to the Health Improvement Network, which is considered generally representative of the country.

They identified a cohort of 2,051,403 children aged 0 to 17 years registered to the database from January 1, 2008 to December 31, 2016. Of these, 12,277 had a new vitamin D prescription.

From 2008 to 2016, the crude annual incidence of vitamin D prescriptions increased from 10.8 to 276.8 per 100,000 person years.

Girls received more prescriptions than boys, for a male-to-female prescribing rate of 1:1.5 across all periods. The increase in prescriptions was greater in older children. Non-white ethnicity and social deprivation also increased the likelihood of vitamin D prescriptions.

The proportion of children getting vitamin D prescriptions who had laboratory-confirmed vitamin D deficiency (25(OH)D < 25 nmol/L) increased from 25.7% to 40.9% between 2008 and 2011, when guidelines changed, then gradually decreased to 27.2%.

During the study period, increased prescribing of vitamin D supplementation was observed in children with "insufficient status" (25(OH)D of 25-50 nmol/L), increasing from 15.8% to 21.7% between 2008 and 2011 to 27.9% to 37.1% during the years 2012 to 2016.

Looking at doses, the investigators considered doses of 280 to 400 international units (IU) to be prevention doses. Doses between 401 and 1000 IU were considered a separate prevention dose, since there is disagreement in the medical community about what constitutes a prevention dose.

The investigators considered doses between 1001 and 10,000 IU/day to be "pharmacological treatment" doses.

The proportion of children with deficiency who received pharmacologic treatment doses increased yearly from 3.8% in 2008 to 79.4% in 2016 (P < .001), which is consistent with UK recommendations.

The proportion of pharmacologic treatment doses also increased among those children with 25(OH)D concentrations between 25 and 50 nmol/L, although UK guidelines say this population should have received prevention doses. Children whose serum vitamin D status was not recorded also experienced an increase in prescriptions at pharmacologic doses.

In the 90 days after initiation of vitamin D supplementation, only 9% of children had 25(OH)D concentrations recorded. Among those whose vitamin D levels were checked, the proportion with 25(OH)D concentrations above 50 nmol/L increased from 11.1% to 76.3%.

The findings suggest that UK physicians are not closely following guidelines on vitamin D.

If prescriptions at prevention doses, and supplementation exceeding recommended doses, were avoided, a total of 32.3% of prescriptions recorded in this study would not have been given, the authors explain. They estimate the potential annual savings at £500,000 ($660,000 US).

Funding came from the UK National Institute for Health Research and the Wellcome Trust. The researchers have disclosed no relevant financial relationships.

BMJ Open. Published online December 3, 2019. Full text

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