Discussion
In this study of young healthy children 1–3 years of age living in Toronto, Canada, we found that children of South Asian and West Asian/North African maternal ethnicities had higher odds of ID, while children of East Asian maternal ethnicity had lower odds of ID when compared with children of European maternal ethnicity. While the overall prevalence of ID was 12.2% in our cohort, the prevalence differed by maternal ethnicity: 20.1% South Asian, 20.9% West Asian/North African and 4.8% East Asian.
Regarding infant feeding practices considered risk factors for ID in young children, we found that children of South Asian maternal ethnicity had higher odds of bottle use beyond 15 months of age, and lower odds of meat consumption in the last 3 days, which may partly explain the higher prevalence of ID among children of South Asian maternal ethnicity. Children of West Asian/North African maternal ethnicity were not found to have higher odds of infant feeding practices considered risk factors of ID. There may be other risk factors we did not examine that may explain the higher prevalence of ID among this group.
There are no nationally representative data of iron status for Canadian children under 3 years of age.29 However, a published review of 10 studies suggests a prevalence of ID ranging from 12% to 63.5%, and for IDA ranging from 1.3% to 79%, depending on the study population, child age and year.4 Many of these studies focused on remote Indigenous communities across Canada, which had high prevalence of childhood ID and IDA.30–34 The lack of access to nutritious and affordable iron-rich foods in these remote communities has been identified as a key determinant of this high prevalence.30 33 35 The other studies focused on children living in urban Canadian settings, but these studies are now more than 20 years old.10 35–38 Given the changes in Canadian demographics, current data are needed.17 Our contemporary cohort demonstrates that while ID is a preventable micronutrient deficiency, it remains persistent among urban Canadian children.
Only one previous Canadian study focused on the association between maternal ethnicity and ID in urban children, and was published more than 30 years ago.10 This study was conducted within a cohort of Chinese children with predominantly immigrant parents, and identified a prevalence of ID of 12.1%. Among infants 6 to 12 months of age, ID was more common in those who were breastfed compared with those who were formula-fed. The authors speculated that excessive amounts of cow’s milk before 12 months of age contributed to the development of ID. In contrast, in our contemporary cohort, controlling for sociodemographic factors, the prevalence of ID was lowest among children of East Asian maternal ethnicity, and feeding practices were not significantly different from those of the European maternal ethnic group.
The few studies examining the association between maternal ethnicity and iron status in children living in other high income, ethnically diverse countries such as the UK and USA were also conducted decades ago. In the UK, D’Souza et al found that serum ferritin levels were lower in children of West Indian and Asian ethnicity, compared with Caucasian children in a small study conducted more than 30 years ago.11 In another UK study, Lawson et al sampled 2-year old children (n=1057) of South Asian parents (Pakistani, Bangladeshi, Indian) 25 years ago.12 Approximately 40% had ID, with risk factors including volume of cow’s milk consumed, use of a bottle and mother’s birth outside of the UK.
In the USA, Brotanek and colleagues examined ID in children 1 to 3 years, with data from more than 15 years ago.13–16 Secular trends in prevalence were examined across three racial groups (non-Hispanic white, non-Hispanic black and Hispanic) using data from the US National Health and Nutrition Examination Survey, over three survey waves (1976 and 2002).16 ID prevalence remained unchanged in non-Hispanic white children at about 6%; unchanged and persistently higher in Hispanic children at about 15%; and decreasing in non-Hispanic black children from approximately 15% to 6% (approximating non-Hispanic white children). Risk factors for the higher prevalence in children of Hispanic race/ethnicity were obesity, not attending daycare and prolonged bottle use.13–16
Therefore, the literature suggests that while the ethnic origins of populations in Canada, the UK and the USA may differ; ID in early childhood remains prevalent. The relationships with maternal ethnicity may also differ; however, several factors appear to be associated with ID across countries and over time. In our current Canadian cohort, we have previously identified several infant feeding practices and nutritional factors associated with increased odds of ID including bottle feeding beyond the first year of life, cow’s milk intake greater than two cups per day, longer total breastfeeding duration, consumption of meat and meat alternatives less than two times per day, and higher body mass index.5–9 25
Strengths of this study include the use of a large sample of healthy children attending a scheduled health supervision visit. Additionally, we included covariates, to adjust for potential confounding and used multiple imputation to address missing covariate data. There are limitations to this study that should be acknowledged. First, although this was a multiethnic cohort, children with non-European maternal ethnicity accounted for approximately 35% of the cohort, compared with 51.5% of the population of Toronto, according to the Canadian census.17 However, our cohort included children with a range of maternal ethnicities, including the largest groups represented in the City of Toronto. Second, we excluded parents who were unable to communicate in English, which may have underestimated the effect of maternal ethnicity. However, less than 7% of children were ineligible to participate in the TARGet Kids! cohort on the basis of a language barrier.18 Finally, the responses to questions regarding infant feeding practices were parent-reported, raising the possibility of recall bias. However, our parent-reported responses are likely valid and reliable given the short recall period (less than 3 years).26
Findings from our study have implications for practice and policy. With many Western countries becoming increasingly diverse, understanding differences in health outcomes by maternal ethnicity will allow for increased cultural competency among healthcare professionals providing care for infants. Examining the associations between ethnicity and health outcomes will also allow for the identification of groups with higher risks of developing disease.39 Culturally tailored health promotion practices will not only allow for a better understanding of a child’s health outcomes but will also increase trust and open communication between parents and healthcare providers.40