Association between cord blood 25-hydroxyvitamin D concentrations and respiratory tract infections in the first 6 months of age in a Korean population: a birth cohort study (COCOA).
OBJECTIVE
Previous studies suggest that the concentration of 25-hydroxyvitamin D [25(OH)D] in cord blood may show an inverse association with respiratory tract infections (RTI) during childhood. The aim of the present study was to examine the influence of 25(OH)D concentrations in cord blood on infant RTI in a Korean birth cohort.


METHODS
The levels of 25(OH)D in cord blood obtained from 525 Korean newborns in the prospective COhort for Childhood Origin of Asthma and allergic diseases were examined. The primary outcome variable of interest was the prevalence of RTI at 6-month follow-up, as diagnosed by pediatricians and pediatric allergy and pulmonology specialists. RTI included acute nasopharyngitis, rhinosinusitis, otitis media, croup, tracheobronchitis, bronchiolitis, and pneumonia.


RESULTS
The median concentration of 25(OH)D in cord blood was 32.0 nmol/L (interquartile range, 21.4 to 53.2). One hundred and eighty neonates (34.3%) showed 25(OH)D concentrations less than 25.0 nmol/L, 292 (55.6%) showed 25(OH)D concentrations of 25.0-74.9 nmol/L, and 53 (10.1%) showed concentrations of ≥75.0 nmol/L. Adjusting for the season of birth, multivitamin intake during pregnancy, and exposure to passive smoking during pregnancy, 25(OH)D concentrations showed an inverse association with the risk of acquiring acute nasopharyngitis by 6 months of age (P for trend=0.0004).


CONCLUSIONS
The results show that 89.9% of healthy newborns in Korea are born with vitamin D insufficiency or deficiency (55.6% and 34.3%, respectively). Cord blood vitamin D insufficiency or deficiency in healthy neonates is associated with an increased risk of acute nasopharyngitis by 6 months of age. More time spent outdoors and more intensified vitamin D supplementation for pregnant women may be needed to prevent the onset of acute nasopharyngitis in infants.
Department of Pediatrics, Gangnam CHA Medical Center, CHA University School of Medicine, Seoul, Korea.
Youn Ho
YH
Shin
Jinho
J
Yu
Kyung Won
KW
Kim
Kangmo
K
Ahn
Seo-Ah
SA
Hong
Eun
E
Lee
Song-I
SI
Yang
Young-Ho
YH
Jung
Hyung Young
HY
Kim
Ju-Hee
JH
Seo
Ji-Won
JW
Kwon
Byoung-Ju
BJ
Kim
Hyo-Bin
HB
Kim
Jung Yeon
JY
Shim
Woo Kyung
WK
Kim
Dae Jin
DJ
Song
So-Yeon
SY
Lee
Soo Young
SY
Lee
Gwang Cheon
GC
Jang
Dong In
DI
Suh
Hyeon-Jong
HJ
Yang
Bong Sung
BS
Kim
Suk-Joo
SJ
Choi
Soo-Young
SY
Oh
Ja-Young
JY
Kwon
Kyung-Ju
KJ
Lee
Hee Jin
HJ
Park
Pil Ryang
PR
Lee
Hye-Sung
HS
Won
Soo-Jong
SJ
Hong
Cohort studies; Infant; Respiratory tract infections; Umbilical cord blood; Vitamin D