There is a growing body of evidence that low vitamin D levels in adulthood are associated with a wide variety of adverse health outcomes. A recent meta-analysis of 18 adult randomized controlled trials found a 7% reduction in all cause mortality in adults randomized to vitamin D containing interventions. Emerging pediatric evidence from cross-sectional or retrospective studies suggests that low vitamin D levels early in life may be related to common child health outcomes often seen by primary care physicians.
We have developed a cohort of over 2000 children between 1 and 5 years of age with detailed clinical, anthropometric and laboratory data using a novel primary care practice based research network called TARGet Kids! In this 4-year longitudinal cohort study we will follow these children’s vitamin D levels and health outcomes during their regularly scheduled primary healthcare visits. Using well established prospective cohort study methodology this will be the first large, prospective study to assess the relationship of vitamin D status and the subsequent development of common adverse child health outcomes including fractures, asthma, respiratory infections, obesity and hypertension.
The primary objective is to determine whether low vitamin D level (25-hydroxyvitamin D < 75 nmol/L as defined by the Canadian Paediatric Society) in children 1-5 years of age is associated with the subsequent development of fractures, asthma, increased asthma severity, viral upper respiratory tract infections, lower respiratory tract infections, obesity or hypertension.
Secondary objectives include determining whether there is a vitamin D dose response relationship with adverse health outcomes by:
- Determining whether children with persistently low vitamin D level (low vitamin D level at more than one time point) are at higher risk of these adverse health outcomes than children with transiently low vitamin D level (low vitamin D level at only one time point).
- Determining whether children with lower vitamin D levels (as a continuous variable) are at higher risk of these adverse health outcomes.