关键词: 呼吸道感染, 维生素D, 儿童, LL-37, 治疗结果

Abstract: Background　Epidemiological surveys show that about 1 billion people worldwide suffer from vitamin D deficiency，which is particularly serious in China.Recurrent upper respiratory tract infection （URTI），with vitamin D deficiency a trigger，is a common and frequently-occurring disease in children，seriously affecting their physical and mental health.Vitamin D deficiency is the main reason for the down regulation of LL-37.As an important incentive，vitamin D deficiency has drawn more and more attention.Objective　To explore the changes in LL-37 level in children with recurrent URTI after vitamin D supplementation.Methods　54 children with recurrent URTI and vitamin D deficiency were selected from the outpatient clinic of Affiliated Hospital of Hebei University from May to November 2017.They were equally randomized into the experimental group and control group，receiving regular treatment with vitamin D supplementation，regular treatment with placebo，respectively.All of them were followed up for 12 months.Episodes of URTI before treatment and during the follow-up period，plasma 25-hydroxyvitamin D3 and LL-37 in sputum supernatant before treatment and at the end of the follow-up were measured and recorded.Results　Forty-five cases completed the follow-up （23 in the experimental group，and 22 in the control group）.Before treatment，both groups showed no significant differences in episodes of URTI，plasma 25-hydroxyvitamin D3 and LL-37 in sputum supernatant （P>0.05）.After 12 months of treatment，episodes of URTI were less，and plasma 25-hydroxyvitamin D3 and LL-37 in sputum supernatant were much higher in the experimental group （P<0.05）.Self-controlled comparisons showed that episodes of URTI，plasma 25-hydroxyvitamin D3 and LL-37 in sputum supernatant changed insignificantly in the control group （P>0.05），while episodes of URTI decreased，and plasma 25-hydroxyvitamin D3 and LL-37 in sputum supernatant increased significantly in the experimental group （P<0.05）.Pearson correlation analysis showed that there was a positive correlation between 25-hydroxyvitamin D3 and LL-37 after one-year treatment in the experimental group （r=0.505，P<0.05）.Conclusion　Vitamin D supplementation helps reduce the possibilities of having recurrent URTI，which may be associated with the increase in LL-37 production.

Key words: Respiratory tract infections, Vitamin D, Child, LL-37, Treatment outcome