The effect of ultraviolet radiation on the 25(OH)D in the blood serum of the population of the Sverdlovsk region

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The effect of ultraviolet radiation on the vitamin D status in the domestic scientific literature is not reflected in sufficient detail, and therefore this work is devoted to the study of the pat terns of solar influence on the status of vitamin D in the blood serum of the population on the example of the Sverdlovsk region. Correlation analysis was carried out between the Sun altitude at noon in the middle of each month and the average level of 25(OH)D, as well as the prevalence of severe vitamin D deficiency in each month, in ten age groups of the Sverdlovsk region residents: 0–4, 5–8, 9–12, 13–16, 17–20, 21–24, 25–28, 29–60, 61–70, 71–80 years. A total of 86130 anonymized measurements of the level of 25(OH)D were analyzed in 2020–2022 and placed at our disposal by INVITRO-Ural LLC, for which the authors express their deep gratitude to its employees. A feature of this study is that the effect of the Sun altitude not only of the current, but also of the previous five months on the average level of 25(OH)D in the blood serum of the population and the prevalence of severe deficiency in the current month was studied, that is, a method was used that in foreign literature is called «lagging correlation» or just «lag». The results of the calculations showed that in the Sverdlovsk region, solar UV radiation is very significant, statistically significantly correlated with the status of vitamin D, while the highest degree of association between the level of 25(OH)D in the blood serum and the prevalence of severe vitamin D deficiency occurs with a lag of 44 and 48 days, respectively. In our opinion, the magnitude of the lag is most likely due to the duration of the period of accumulation of a fairly stable level of 25(OH)D in human serum in early to mid-summer, when in the northern hemisphere the Sun altitude is at an effective level close to 50 °. The value of the lag at which there is the greatest association between the Sun altitude and the status of vitamin D (the level of 25(OH)D and the prevalence of severe deficiency) is statistically significantly reduced in the groups of the older population of the Sverdlovsk region, which may be due to the increased prevalence of vitamin D deficiency in this category of the population, the presence of which implies a faster reaction of the body to external influences.