Introduction: NSW was subject to lockdown public health stay-at-home orders in 2020. Vitamin D is primarily derived from synthesis through the skin. The lockdown was associated with limited exposure to the sun. The aim of this study was to determine whether the COVID-19 stay-at-home orders were associated with lower serum vitamin D levels in NSW, compared with the previous 5-year average.
Methods: This study is a retrospective observational study of pathology results measuring serum vitamin D levels in the Southern IML pathology database. The study compared serum vitamin D levels between 30 Mar and 13 June in 2015–2019, to the same period in 2020 that coincided with lockdown, using an exploratory generalised linear model. This study had a large sample size of 279,341 samples across multiple patient demographics.
Results: There was a significant reduction in serum vitamin D during lockdown period (χ2= 77.746, df=2; p <.001), which was more pronounced among males (males: Δ=-5.37 nmol/L; females: Δ=-3.83 nmol/L; χ2=9.362, df=1; p <.001).
Conclusion: This study observed a significant reduction in the serum vitamin D values in the NSW 2020 lockdowns. Further investigation is required to elucidate these findings and moderating factors.