Comparative analysis of vitamin D levels in young men in different climatic and geographical regions of the Russian Federation

Vitamin D deficiency remains a significant public health problem in the Russian Federation, especially among the young population in the northern regions, underscoring the necessity to investigate the factors that determine its level. Objective. To compare serum concentrations of 25-hydroxyvitamin D in adolescent males living in different climatic and geographical regions of Russia and to evaluate the impact of climatic factors on this parameter, considering their interaction effects. Materials and methods. The study included 190 young males (aged 17 to 21 years) who were natives of three regions: the Northeast (Magadan, n=97), the Northwest (Murmansk, n=43), and Central Russia (Moscow, n=50). Serum concentrations of 25-hydroxyvitamin D were measured using an immunochemical method. Multiple linear regression analysis was performed to evaluate the association between vitamin D status and climatic indicators. Results. Significantly lower serum 25-hydroxyvitamin D concentrations were found in young males from the Northwest (15.53 [11.5; 24.1] ng/ml) and Northeast (18.4 [14.7; 23.1] ng/ml) compared to their peers from Central Russia (23.5 [18.9; 29.8] ng/ml; p<0.001). The vitamin D deficiency rate in the northern groups reached 59—61%, which was significantly higher than in the Central region (32%). Dietary vitamin D intake in all groups was below the recommended physiological level and did not correlate with its serum concentration. The regression model showed a statistical significance (p<0.001), but it accounted for only 12.3% of the variance in the dependent variable. Statistically significant interaction effects between climatic factors were identified: «sunny days × cloud cover» (β=0.155; p<0.001) and «sunny days × temperature» (β=0.006; p=0.05), indicating a synergetic nature of their combined influence. Conclusion. A pronounced 25-hydroxyvitamin D deficiency was revealed in young males from the northern regions of Russia along with inadequate dietary intake. Climatic factors have a non-linear impact and require mandatory consideration of interaction effects. The low explanatory capacity of the model justifies the need to include individual behavioral and environmental factors in future studies.