The Variability of Vitamin D Concentrations in Short Children with Short Stature from Central Poland—The Effects of Insolation, Supplementation, and COVID-19 Pandemic Isolation

The aim of the study was to investigate effects seasonal variability insolation, implementation new recommendations for vitamin D supplementation (2018), and SARS-CoV-2 pandemic lockdown (2020) on 25(OH)D concentrations in children from central Poland. retrospective analysis during last 8 years performed a group 1440 with short stature, aged 3.0–18.0 years. Significant differences were found between periods mid-2014 mid-2018, mid-2018 mid-2020, mid-2020 mid-2022 (medians: 22.9, 26.0, 29.9 ng/mL, respectively). Time series models created grounds data 6 pre-pandemic period used prediction explained over 80% concentrations, overprediction first year underprediction second year. A significant increase observed both after introduction guidelines pandemic; however, scale deficiency insufficiency still too high. are useful analyzing impact health policy interventions restrictions concentrations.