Vitamin D status in an Australian patient population: a large retrospective case series focusing on factors associated with variations in serum 25(OH)D

Veronica Tsin Fong Voo; Jim Stankovich; Terence J O'Brien; Helmut Butzkueven; Mastura Monif

doi:10.1136/bmjopen-2019-032567

Vitamin D status in an Australian patient population: a large retrospective case series focusing on factors associated with variations in serum 25(OH)D

BMJ Open. 2020 Mar 4;10(3):e032567. doi: 10.1136/bmjopen-2019-032567.

Authors

Veronica Tsin Fong Voo^{1

2

3}, Jim Stankovich², Terence J O'Brien^{2

3}, Helmut Butzkueven^{2

3}, Mastura Monif^{4

2

3}

Affiliations

¹ Department of Physiology, University of Melbourne, Parkville, Victoria, Australia.
² Department of Neuroscience, Monash Univeristy, Melbourne, Victoria, Australia.
³ Department of Neurology, Royal Melbourne Hospital, Parkville, Victoria, Australia.
⁴ Department of Physiology, University of Melbourne, Parkville, Victoria, Australia mastura.monif@monash.edu.

Abstract

Objectives: To investigate whether sex, age, medical specialty and seasonal variations in serum concentration of 25-hydroxy vitamin D (25(OH)D) are evident among an Australian patient population.

Design: Retrospective study analysing the results of serum 25(OH)D lab tests and vitamin D supplementation from Royal Melbourne Hospital (RMH) between 2014 and 2017.

Setting: Tertiary healthcare centre in Victoria, Australia.

Participants: 30 023 patients (inpatient and outpatient) who had their serum 25(OH)D levels measured at RMH between 2014 and 2017.

Main outcome measures: Serum 25(OH)D levels stratified according to patients' sex, age and medical specialty admitted to, as well as the season and year (2014 to 2017) 25(OH)D level was measured.

Results: Mean serum 25(OH)D level of study population was 69.9 nmol/L (95% CI 69.5 to 70.2). Only 40.2% patients in this cohort were sufficient in vitamin D (>75 nmol/L). On average, 25(OH)D levels in male patients were 6.1 units (95% CI 5.4 to 6.9) lower than in females. Linear regression analysis found that 25(OH)D levels increased by 0.16 unit (95% CI 0.14 to 0.18) for every year increase in age. One-way analysis of variance showed patients from neurology had the highest average 25(OH)D level, 76.8 nmol/L (95% CI 74.2 to 79.3) compared with other medical specialties. Mean 25(OH)D level during winter, 64.9 nmol/L (95% CI 64.2 to 65.6) was significantly lower compared with other seasons despite supplementation. Average 25(OH)D level measured in 2014, 71.5 nmol/L (95 CI% 70.8 to 72.2) was significantly higher than levels measured in 2016-2017.

Conclusions: There is a sex, age, medical specialty, seasonal and yearly variation in vitamin D status in an Australian patient population. The association between low vitamin D status and winter despite supplementation suggests other interventions are required to boost serum 25(OH)D levels.

Keywords: Australian cohort study; epidemiology; patient population; vitamin D.

MeSH terms

Adult
Aged
Female
Health Status*
Humans
Male
Middle Aged
Retrospective Studies
Seasons
Tertiary Healthcare / statistics & numerical data*
Victoria / epidemiology
Vitamin D / analogs & derivatives*
Vitamin D / blood
Young Adult

Substances

Vitamin D
25-hydroxyvitamin D