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OBJECTIVE: dose has beneficial effects on sleep until 2 years of age and whether early life 25(OH)D is associated with sleep. METHODS: supplementation of 400-IU (n = 421) or 1200-IU (n = 424) daily until 24 months of age. Blood 25(OH)D was analyzed and parents completed questionnaires at 11.7 (SD = 0.7) and at 26.0 (SD = 3.0) months (Brief Infant Sleep Questionnaire, Sleep Disturbance Scale for Children). Maternal 25(OH)D was analyzed at mean 11.3 (SD = 2.2) gestational weeks. We used regression models adjusted for season of birth, breastfeeding, gestational age, parental education, and mother's age, body-mass-index, smoking and sleep. RESULTS: High-dose versus standard-dose supplementation was not associated with child's sleep up to 24 months. Children with 25(OH)D ≥ 75 nmol/L at 12 months had less sleep disturbances at 24 months (adjusted for all covariates: B = -1.46 points 95 % CI: 2.89; -0.04, p = 0.05), especially disorders of arousal (B = -0.40, 95 % CI: 0.64;-0.15, p = 0.002). We also found associations between maternal 25(OH)D ≥ 75 nmol/L during pregnancy and child's more favorable sleep characteristics. CONCLUSION: provides no benefits for child's sleep, even if we found an association between child's higher 25(OH)D and less sleep disturbances. Higher maternal 25(OH)D during pregnancy was associated with child's better sleep, which should be studied further.
Seppälä et al. (Mon,) studied this question.