Prevalence of Vitamin D deficiency in the North-West region of Russia: A cross-sectional study.

Russia is a country with geographic and economic preconditions for development of vitamin D deficiency. We analyzed serum 25(OH)D level in residents from North-West region (59-61° North latitude) of Russia to study the prevalence of vitamin D insufficiency and deficiency and its associations with gender, age, obesity and diet. The study population included 1664 residents (1544 adults 18-75 y.o. and 120 children/adolescents of 3-17 y.o.). Serum 25(OH)D was determined in 1226 participants by electrochemiluminescence immunoassay. We used a questionnaire to check the frequency of dairy and fish products intake as well as the use of vitamin supplements. The serum 25(OH)D level was 9.8-147.5nmol/L, mean level in adults population was 54.8±0.7nMol/L, in children/adolescents-46.8±1.6 nmol/L. We revealed that 16.8% of the study population had a 25(OH)D level more than 75nMol/L, 37.5% had insufficiency and 45.7% had vitamin D deficiency. Serum 25(OH)D level in women was lower than in men (53.9±0.8 and 67.2±2.2nmol/L; p<0.01). We did not find association between vitamin D status and age. Patients with normal BMI had higher 25(OH)D level than those with overweight and obesity (52.5±2.8 and 44.8±2.0 nmol/L, p<0.05). Negative correlations between 25(OH)D and BMI (r=-0.17, p=0.03) and WC (r=-0.15, p=0.02) were found. Questionnaire analyses showed that regular fish intake (minimum once per week) was associated with higher 25(OH)D level, while dairy products and vitamin supplements intake did not seem to have any effect on vitamin D status. This study showed high prevalence of vitamin D insufficiency and deficiency in adults and adolescent population from North-West region of Russia, and an association of low serum 25(OH)D level with female gender, obesity and low fish products diet.