Seasonal variations in serum vitamin D levels in children and adults with various diseases

Objective. To assess serum 25(OH)D levels in patients with various diseases living in Moscow and the Moscow region, considering the season of the year and age. Patients and methods. A cross-sectional uncontrolled diagnostic trial was performed. It included 10.707 people: 8,441 (78.8%) women and 2,266 (21.2%) men; children accounted for 15% (1,501 children) and adults – for 85% (9,206 people); the mean age of adults was 49.86 ± 21.92 years and that of children – 13.45 ± 11.76 years. Results. The maximum prevalence of severe 25(OH)D deficiency was revealed among patients with neoplasms (48.9%); patients with diseases of the musculoskeletal system and connective tissue had severe 25(OH)D deficiency in 16.9% of cases, with urogenital diseases – in 19.6% of cases, with digestive diseases – in 19.0% of cases, with perinatal diseases – in 15.7% of cases, with diseases of blood and hematopoietic organs – in 22.3% of cases, which proved to be 2-3 times more frequent compared to individuals with diseases of other classes. Individuals who underwent preventive examination had the lowest prevalence (1.4%) of severe 25(OH)D deficiency. In case of diseases with chronic progressive autoimmune inflammation (type 1 diabetes mellitus (DM), rheumatoid arthritis (RA)), neoplasms, as well as in complications of diseases of various pathogenesis, such as chronic kidney disease (CKD), vitamin D deficiency was observed throughout the year, which did not correspond to increasing daylight hours. Children with perinatal diseases and born preterm had low levels and severe deficiency of 25(OH)D, which occurred immediately after birth. Conclusion. The prevalence of vitamin D deficiency was 82.9%; the lowest serum 25(OH)D levels were recorded in winter and spring. Severe year-round serum 25(OH)D deficiency was revealed in patients with autoimmune diseases and chronic kidney disease. Key words: adults, vitamin D, inflammation, 25(OH)D, children, deficiency, seasons of the year