title: Low Serum Levels of Vitamins A, D, and E Are Associated with Recurrent Respiratory Tract Infections in Children Living in Northern China: A Case Control Study.
abstract: BACKGROUND
  This study aimed to investigate the association of serum concentrations of vitamin A, D, and E with recurrent respiratory tract infections (RRTIs).
  
  
  METHODS
  A total of 1200 children aged at 0.5-14 years were selected via a face-to-face survey in Harbin, China. Among the participants, 600 children with RRTIs comprised the symptomatic group (RRTI group), whereas 600 healthy children were used as controls (control group). Blood samples were collected to measure serum levels of vitamins A and E by HPLC; the serum level of 25-hydroxycholecalciferol (25(OH)D), was measured by HPLC-MS/MS.
  
  
  RESULTS
  Serum levels of vitamins A and E, as well as 25(OH)D, were significantly lower in the RRTI group than the control group. The conditional logistic regression model and the receiver-operating characteristic curve showed that the insufficiency or deficiency of vitamins A, D, and E was positively correlated with RRTI occurrence (p < 0.05).
  
  
  CONCLUSIONS
  Low serum concentrations of vitamins A, D, and E were associated with RRTIs in children from northern China.
authors.affiliation: Department of Clinical Nutrition, Harbin Children's Hospital, Harbin, China.
authors.forename: Xuguang
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Clinical Nutrition, Harbin Children's Hospital, Harbin, China.
authors.forename: Fengshu
authors.initials: F
authors.lastname: Ding
authors.affiliation: Department of Clinical Nutrition, Harbin Children's Hospital, Harbin, China.
authors.forename: Huaining
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Clinical Laboratory, Harbin Children's Hospital, Harbin, China.
authors.forename: Wenfeng
authors.initials: W
authors.lastname: Zhao
authors.affiliation: Department of Clinical Nutrition, Harbin Children's Hospital, Harbin, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Jing
authors.affiliation: Department of Clinical Nutrition, The first Affiliated Clinical Hospital of Harbin Medical University, Harbin, China.
authors.forename: Yageng
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Department of Clinical Nutrition, Harbin Children's Hospital, Harbin, China.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D012008:Recurrence; D012141:Respiratory Tract Infections / Q000097:blood* / Q000453:epidemiology*; D011795:Surveys and Questionnaires; D014801:Vitamin A / Q000097:blood*; D014807:Vitamin D / Q000097:blood*; D014810:Vitamin E / Q000097:blood*
chemical_list: D014801:Vitamin A; D014807:Vitamin D; D014810:Vitamin E