Association between vitamin D status and incidence of respiratory infections in infants and young children

Background. The incidence of respiratory infections (RI) among children has been high for many years. Vitamin D deficiency may be one factor in this increased frequency of infections in children. The high prevalence and lack of outward manifestations of vitamin D deficiency may explain the low recognition of this condition.

Aim. Assessment of the relationship of vitamin D status with the incidence of RI in infants and young children.

Materials and methods. The study included 94 children aged 4.5–18 months (mean age – 10.9±2.66 months). We determined vitamin D levels in infants and young children and the number of RI episodes in the first six months of life. The children belonged to health groups I and II. The association between the incidence of RI and vitamin D levels was analyzed: the average values of vitamin D levels in children in subgroups with different frequencies of RI were determined, and a critically significant vitamin D level associated with the development of 4 or more episodes of respiratory tract infections during the follow-up period was revealed.

Results. The average blood vitamin D level in children was 48.33±21.16 ng/ml. Vitamin D deficiency was detected in 5 (5%) children, and insufficiency was found in 14 (15%). Children with one disease in the first six months of life had the highest average vitamin D levels – 57.1 (49.4–69.7; CI 95%) ng/ml, which was statistically significant in comparison with the group of children with three or more diseases – 38,1 (36,9–60,1; CI 95%) ng/ml. The vitamin D level was determined to be 37 ng/ml, a decrease in which is associated with a statistically significant increase in the incidence of RI – more than 4 episodes in 6 months.

Conclusion. Vitamin D deficiency and insufficiency in children are associated with more frequent episodes of RI. Vitamin D levels below 37 ng/ml are associated with frequent episodes of acute RI in the first six months of life (more than five episodes per six months). Thus, the frequency of RI may be a marker of vitamin D deficiency or insufficiency in the absence of clinical symptoms affecting the musculoskeletal system.