Lower Adherence to Vitamin D Prophylaxis in Families With Multiple Children

ABSTRACT Aim This study investigated whether family composition and other household factors are associated with adherence to vitamin D supplementation during infancy. Methods A cross‐sectional survey was conducted between March 21 and April 30, 2023, among caregivers of infants aged 4 weeks to 12 months at the Ca′ Granda Hospital, Milan, Italy. The survey investigated demographic data, health status, daily vitamin D 3 administration frequency, and family characteristics. Multiple logistic regression was used to identify factors associated with poor adherence. Results A total of 241 caregivers completed the survey. Overall, 85% of infants received vitamin D supplements at least four times per week. Good adherence was more frequent in families with one child (91%) compared with those with two or more children (78%). In multivariable analysis, the presence of siblings was the only factor significantly associated with poor adherence (odds ratio 2.72, 95% confidence interval 1.25–5.92). No associations were found with caregiver education, infant age, chronic disease, intercurrent illness, or time spent outdoors. Conclusion In this cohort, adherence to vitamin D prophylaxis was significantly lower in families with more than one child. Awareness of this association could inform counselling strategies and the design of interventions to sustain adherence.