Race differences in the association between multivitamin exposure and wheezing in preterm infants.

OBJECTIVE: We aimed to determine whether vitamin D exposure, as estimated by use of multivitamins, is positively or negatively associated with recurrent wheezing in infants born preterm. STUDY DESIGN: This prospective cohort study enrolled 300 infants, born at 28(0/7) to 34(6/7) weeks gestational age, and conducted follow-up at 3-, 6-, 9- and 12-month adjusted age. RESULT: Black (55.9%) and non-black (36.6%) infants experienced recurrent wheezing. Adjusted odds ratios (ORs) for the association between multivitamin exposure at 3 months and recurrent wheezing were 2.15 (95% confidence interval (CI): 0.97, 4.75) for black and 0.43 (95% CI: 0.19, 0.96) for non-black infants with an interaction by race (P=0.003). In lag-effect models, ORs were 2.69 (95% CI: 1.41, 5.14) for black and 0.50 (95% CI: 0.27, 0.92) for non-black infants. CONCLUSION: Differences by race were seen in association between multivitamins and wheezing; population heterogeneity should be considered when evaluating vitamin supplementation.

Relation between sleep duration and BMI varies by age and sex in youth age 8-19.

OBJECTIVES: The objectives of this study were to (i) compare the strength of associations between sleep duration and body mass index (BMI) in middle childhood, and early and late adolescence; (ii) determine whether sleep duration in middle childhood predicts BMI in early or late adolescence; and (iii) examine the consistency of these associations by sex. METHODS: Subjects included 313 children/adolescents aged 8-19 participating in a longitudinal cohort study on sleep and health. Participants were assessed at three time points approximately 4 years apart: ages 8-11, 12-15 and 16-19. BMI z-score (BMIz) was calculated using age and sex normative data from the Centers for Disease Control. Sleep duration was reported by the parent (ages 8-15) or the adolescent (ages 16-19). RESULTS: [corrected] Half of the participants were male and 79% were Caucasian. Sleep duration had a negative linear association with BMIz for boys but not girls, and the magnitude of this association decreased with age. Sleep duration at age 8-11 predicted BMIz in early and late adolescence for boys but not girls, and associations were largely attenuated after adjusting for BMIz at age 8-11. The strongest predictor of adolescent BMIz was BMIz at age 8-11 for both boys and girls. CONCLUSION: We conclude that the association between sleep duration and BMIz varies by sex and age, with stronger associations in boys and in middle childhood compared with adolescence.