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Trends in the incidence of testing for vitamin D deficiency in primary care in the UK: a retrospective analysis of The Health Improvement Network (THIN), 2005–2015
  1. Francesca L Crowe1,
  2. Kate Jolly1,
  3. Christine MacArthur1,
  4. Semira Manaseki-Holland1,
  5. Neil Gittoes2,3,
  6. Martin Hewison4,
  7. Robert Scragg3,
  8. Krishnarajah Nirantharakumar1
  1. 1 Institute of Applied Health Research, University of Birmingham, Birmingham, UK
  2. 2 Centre for Endocrinology, Diabetes and Metabolism, University of Birmingham, Birmingham, UK
  3. 3 School of Population Health, The University of Auckland, Auckland, New Zealand
  4. 4 Institute of Metabolism and Systems, University of Birmingham, Birmingham, UK
  1. Correspondence to Dr Francesca L Crowe; F.Crowe{at}


Objective To investigate trends in the incidence of testing for vitamin D deficiency and the prevalence of patients with circulating concentrations of 25-hydroxyvitamin D (25(OH)D) indicative of deficiency (<30 nmol/L) between 2005 and 2015.

Design Longitudinal analysis of electronic health records in The Health Improvement Network primary care database.

Setting UK primary care.

Intervention None.

Participants The analysis included 6 416 709 participants aged 18 years and older.

Primary outcomes Incidence of having a blood test for vitamin D deficiency between 2005 and 2015, the prevalence with blood 25(OH)D <30 nmol/L and the effects of age, ethnicity and socioeconomic status on these measures were assessed.

Results After a mean follow-up time of 5.4 (SD 3.7) years, there were 210 502 patients tested for vitamin D deficiency. The incidence of vitamin D testing rose from 0.29 per 1000 person-years at risk (PYAR) (95% CI 0.27 to 0.31) in 2005 to 16.1 per 1000 PYAR (95% CI 15.9 to 16.2) in 2015. Being female, older, non-white ethnicity and more economically deprived were all strongly associated with being tested. One-third (n=69 515) had 25(OH)D <30 nmol/L, but the per cent deficient among ethnic minority groups ranged from 43% among mixed ethnicity to 66% in Asians. Being male, younger and more economically deprived were also all associated with vitamin D deficiency (p<0.001).

Conclusions Testing for vitamin D deficiency increased over the past decade among adults in the UK. One-third of UK adults who had a vitamin D test performed in primary care were vitamin D deficient, and deficiency was much higher among ethnic minority patients. Future research should focus on strategies to ensure population intake of vitamin D, particularly in at-risk groups, meets recommendations to reduce the risk of deficiency and need for testing.

  • 25-hydroxyvitamin D
  • vitamin D
  • deficiency
  • primary care
  • the health improvement network

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  • Contributors FLC, KJ, CM, SM-H, NG, MH, RS and KN made substantial contributions to the conception and design, acquisition of data or analysis and interpretation of data. All authors drafted the article or revised it critically for important intellectual content. All authors approved the final version of the manuscript to be published. FLC is the guarantor of this work.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Ethics approval Ethics approval was obtained by Scientific Review Committee (for the use of THIN data) in September 2017 (SRC reference 17THIN088).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement The dataset on which the conclusions of the paper rely are available on request from the authors.

  • Patient consent for publication Not required.