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.

Summary Background Early childhood temperament is increasingly recognized as an important attribute that may impact screen time use, outdoor play and childhood obesity. The relationship between temperament and nutrition in preschool children is less clear. Objective The objective of the study is to investigate if temperament dimensions (negative affectivity, effortful control and surgency) in early childhood are associated with nutritional risk factors. Methods Six hundred seventy‐eight children were followed (mean age at baseline visit 3.1 years; mean time to follow‐up 16.5 months). Parents reported on child temperament and nutritional risk factors during regularly scheduled well‐child clinic visits. Results A mixed effect model demonstrated a significant association between higher negative affectivity (1.03; 95% CI 0.69 to 1.37) and higher effortful control (−0.88; 95% CI −1.27 to −0.49) on concurrent nutritional risk, independent of covariates. Multivariate linear regression analysis identified that higher effortful control, and not negative affectivity, was significantly associated with a decrease in nutritional risk (−0.67; 95% CI −1.10 to −0.24) over time, independent of covariates. There was no relationship identified between surgency and nutritional risk. Conclusion Three‐year‐old children with higher effortful control had reduced nutritional risk at 5 years of age. Future nutritional risk prevention strategies may benefit from interventions to increase effortful control in early childhood.

Children who spend more time in daycare have less parent-reported outdoor free play. Parents may be relying on daycare to provide opportunity for outdoor free play and interventions to promote increased active play opportunities outside of daycare are needed.