Grant: Doctoral Award - Frederick Banting and Charles Best Canada Graduate Scholarships

A majority of North American children older than 1 year of age have vitamin D levels lower than either the American Academy of Pediatrics (AAP) or Canadian Paediatric Society (CPS) recommendations. Low vitamin D levels may be associated with some of the most common health issues during childhood including, asthma and upper and lower respiratory tract infections, which account for over 30 percent of all emergency department visits and collectively cost the Canadian health care system millions of dollars annually. The primary objective is to determine whether a low vitamin D level (25-hydroxyvitamin D < 75 nmol/L as defined by the Canadian Paediatric Society) in children 0-5 years of age is associated with increased collective health service utilization (hospitalizations, emergency department visits, and physician visits with the exclusion of routine primary healthcare visits) for asthma, upper respiratory tract infections (URTI) and lower respiratory tract infections (LRTI). The secondary objectives include determining whether low vitamin D levels and oral vitamin D supplementation are associated with increased health service utilization for a) asthma, b) URTIs and c) LRTIs separately. This study will include healthy children ages 0 to 5 years recruited in Toronto, Canada between December 2008 and March 2013 through the TARGet Kids! practice based research network. Health service utilization data will be obtained by linking each child's provincial health card number to health services data at the Institute for Clinical Evaluative Sciences (ICES). For the primary analysis, Poisson regression will be used to determine the association between 25-hydroxyvitamin D and health service utilization. If a low vitamin D level is making even a small contribution to health service utilization for these common health problems, measures to increase vitamin D levels may offer a significant benefit in reducing population wide morbidity and associated health service costs.