Vitamin D exposure during pregnancy, but not early childhood, is associated with risk of childhood wheezing

Abstract

The association between vitamin D and wheezing in early childhood is unclear. The primary objective of this study was to evaluate the association between vitamin D exposure, during both pregnancy and childhood, and early childhood wheezing. Secondary objectives were to evaluate the associations between vitamin D exposures and asthma and wheezing severity. We conducted a cohort study of children (0-5 years) recruited from 2008 to 2013 through the TARGet Kids! primary-care research network. Vitamin D exposures included maternal vitamin D supplement use during pregnancy, child vitamin D supplementation and children's 25-hydroxyvitamin D (25(OH)D) concentrations. The outcomes measured were parent-reported childhood wheezing, diagnosed asthma and wheezing severity. Vitamin D supplement and wheezing data were available for 2478 children, and blood samples were available for 1275 children. Adjusted odds ratios (aOR) were estimated using logistic regression adjusted for age, sex, ethnicity, body mass index, birth weight, outdoor play, breastfeeding duration, daycare status, parental smoking and family history of asthma. Vitamin D supplementation during pregnancy was associated with lower odds of childhood wheezing (aOR=0.65; 95% CI: 0.46-0.93). In early childhood, neither 25(OH)D (aOR per 10 nmol/l=1.01; 95% CI: 0.96-1.06) nor vitamin D supplementation (aOR=1.00; 95% CI: 0.81-1.23) was associated with wheezing. No significant associations were observed with diagnosed asthma or wheezing severity. Vitamin D supplementation during pregnancy was associated with reduced odds of wheezing, but child vitamin D supplementation and childhood 25(OH)D were not associated with reduced wheezing. The timing of exposure may be important in understanding the association between vitamin D and childhood wheezing.

Vitamin D supplementation in primary allergy prevention: Systematic review of randomized and non‐randomized studies

“…No effect of vitamin D was found for any allergy outcome: atopic dermatitis (RR, 0.96; 95% CI, 0.57 to 1.61), asthma and/or wheezing (RR, 1.12; 95% CI, 0.50 to 2.54), allergic rhinitis (RR, 0.76; 95% CI, 0.31 to 1.85), and food allergy (RR, 1.92; 95% CI, 0.57 to 6.50). We also found two NRSs, one cohort and one case‐control, reported development of asthma/wheezing and food allergy, respectively. In the cohort study, vitamin D was associated with low risk of developing wheezing (OR, 0.65; 95% CI, 0.46 to 0.93).…”

“…The certainty in the body of evidence for these two outcomes was very low. The other cohort study suggested no impact of vitamin D supplementation in childhood on asthma/wheezing (OR, 1.00; 95% CI, 0.81 to 1.23).…”

The persistence of maternal vitamin D deficiency and insufficiency during pregnancy and lactation irrespective of season and supplementation

“…During pregnancy and lactation, maternal physiologic adaptations serve to protect calcium homoeostasis for the foetus such that, even in the presence of maternal vitamin D deficiency, the newborn can have normal serum calcium and seemingly normal skeletal health . However, although causality remains unclear, observational studies have linked low maternal vitamin D concentration during this period with adverse effects in the offspring including increased fat mass at age 4 years, decreased bone mineral content at age 9 years, decreased peak bone mass in early adulthood, and a potentially higher incidence of immune‐related illnesses such as asthma and type 1 diabetes . Furthermore, higher vitamin D intake has been associated with a decrease in pregnancy complications and improved birth outcomes .…”

“…Specifically, pregnancy and lactation comprise a unique critical window (i) that spans all seasons (and therefore includes winter) and (ii) during which maternal vitamin D status may affect the health of both mother and child . Indeed, in observational studies, low maternal vitamin D during this window has been associated with subsequent long‐term outcomes in the offspring including increased fat mass at 6 years of age, decreased bone mineral content at 9 years of age, decreased peak bone mass in early adulthood and a potentially higher incidence of immune‐related illnesses such as asthma and type 1 diabetes . Despite its potential importance, however, there has been limited serial evaluation of vitamin D status in women across this critical time period.…”

Special Considerations in Preschool Age

“…Likewise, lower levels of vitamin D in 0-4-year-olds have been associated with acute wheezing [89]. However, this association is debated, as several studies have not observed a link between vitamin D levels and airway function, both regarding maternal intake and the child's intake of vitamin D [90,91]. Meta-analysis results from two randomized controlled trials with a follow-up time of 3 years showed that vitamin D supplementation during pregnancy resulted in a significantly reduced risk of asthma or recurrent wheeze in the offspring (~25% risk reduction by 3 years), especially among women with low vitamin D (25(OH)D level <30 ng/ml) at randomization [88].…”