Seasonal fluctuations of vitamin D in blood serum in different age groups of the Khanty-Mansiysk Autonomous Okrug – Ugra population

Studies of the recent decades indicate the prevalence of insufficient blood vitamin D levels in the population of many regions of the Russian Federation, which varies significantly depending on the age of a person and the season. <b>The aim</b> of the research was to study the seasonal variability of vitamin D status in different age groups of the population of the Khanty-Mansiysk Autonomous Okrug - Ugra. <b>Material and methods</b>. Data on the vitamin D status of the population living in the Khanty-Mansiysk Autonomous Okrug - Ugra in 2020-2022 were obtained based on statistical processing of 31,595 impersonal measurements of calcidiol levels [total 25(OH) D₂ and 25(OH)D₃] in the blood serum of residents of the Autonomous Okrug, carried out in the laboratories of INVITRO-Ural LLC using the chemiluminescent microparticle immunoassay. After rejection, the materials were divided into the following age groups: 0-11 months (n=320), 1-2 years (n=398), 3-6 years (n=881), 7-10 years (n=954), 11-14 years (n=1002), 15-17 years (n=861), 18-20 years (n=661), 21-24 years (n=1137), 25-30 years (n=1704), 31-40 years (n=8708), 41-50 years (n=5310), 51-60 years (n=3686), 61-70 years (n=1997), over 70 years (n=570). <b>Results</b>. In the Khanty-Mansiysk Autonomous Okrug - Ugra, the highest serum concentration of 25(OH)D, which did not fall below 30 ng/ml during the year, was observed in infants (under one year of age). As age increased, serum calcidiol levels decreased in each age group (p<0.0001), and the prevalence of vitamin D deficiency increased. The lowest mean serum calcidiol level (up to 12-14 ng/ml) was observed in the spring months in adolescents and young adults aged 11 to 24 years. In higher age groups, vitamin D status increased gradually, but statistically significantly (p<0.0001). In middle-aged and elderly residents (30-70 years), the average calcidiol level did not fall below 22 ng/ml throughout all seasons, and in summer and autumn it was at a level of 26-29 ng/ml, close to sufficient (30 ng/ml). In residents over 70 years of age, vitamin D status was slightly lower than in the 61-70 age group in winter (p≤0.05), and did not differ in summer, but regardless of the season it was significantly higher (p≤0.001) than in adolescents and young adults. <b>Conclusion</b>. The obtained results allow us to recommend vitamin D supplementation in moderate doses to middle-aged and elderly individuals who do not belong to risk groups during the period of detection of the lowest serum 25(OH)D level from December to May. Adolescents and young adults aged 11 to 24 years need periodic screening of 25(OH)D level in blood serum throughout the year, especially in the winter and spring months, and vitamin D intake in doses that ensure maintenance of serum calcidiol at a level of at least 30 ng/ml.