Prevalence of iron-deficiency anaemia and low iron status and feeding practices among 9 months old infants in Vancouver

Iron-deficiency anaemia (IDA) is considered to be the most common nutritional deficiency among infants and children worldwide. The consequences of IDA on the developing central nervous system may be irreversible; these may include delayed mental and motor development, and reduced school performance. Infants are particularly prone to develop IDA if given foods low in iron content or foods that contain iron of low bioavailability. Infants from low socioeconomic background and Asian, Black or Hispanic infants, are believed to be at higher risk for IDA than White infants. There are no published studies on iron status in relation to feeding history from British Columbia or other parts of Canada. The purpose of this study was to determine the prevalence of IDA and low iron status in 9 month old infants in Vancouver, British Columbia, and to determine which infants are at highest risk for IDA and low iron status based on their feeding history, economic and ethnic background. Infants who could participate in the study were identified from birth and death lists provided by the Vancouver Public Health Department. Eligibility criteria were that the infant was full term (gestational age a: 37-<42 weeks) with a birth weight of 2500-4500g and born between January 1st, and March 2nd, 1993, or between June 4th and August 7th, 1993 to parents resident in Vancouver, with an address to enable contact. Initial contact with parents of all eligible infants (n = 1813) was made through a letter. A subsequent telephone call was made to the parents to describe the study protocol and to arrange an appointment for parents interested in participating with their infant. All the appointments were made to coincide with the time when the infant would be 39 ± 1 weeks old. At the clinic appointment, blood samples were collected from the infants, parents completed questionnaires regarding their family background and their infant's nutritional history from birth to 9 months of age, and a visual recognition memory test (Fagan Test of Infant Intelligence) was administered to the infant. Because many tests used to diagnose iron-deficiency anaemia lack specificity, several tests were used in combination. IDA was classified as a Hgb ^101 g/L or Hgb <110 g/L with 2 or 3 abnormal biochemical tests from serum ferritin :S 10 //g/L, total iron binding capacity > 60 //mol/L, and zinc protoporphyrin >70 //mol ZPP/mol heme. Low iron status was classified as a serum ferritin ^10 //g/L without iron-deficiency anaemia. Four hundred and thirty four (434) 9 month old infants and their parents participated in the study, representing 23.9% of all the eligible infants. The prevalence of IDA and low iron status was 6.9% and 24.4%, respectively. A statistically significant association (p<0.0001) was found between the infants' iron status and the duration of breast-feeding. IDA and low iron status was found in 15.2% and 30.4%, respectively, in infants who had received breastmilk as their main source of milk for more than 8 months. In contrast, the prevalence of IDA and low iron status was 1.5% and 10.3%, respectively, among the group of infants who were never breast-fed. Feeding low iron milk (cows' milk, low iron infant formula or goat's milk) also showed a statistically significant (p < 0.05) association with the iron status of the infants. No statistically significant association was found between iron status and the age of introduction of specific solid foods (iron-fortified infant cereals, fruits, vegetables, legumes, egg yolk, tofu, meat, chicken, or fish), or fruit juice. No statistically significant association was found between the annual family income and iron status of the infants, when considering either the entire group of infants, or the infants from two parent households. However, a statistically significant association (p< 0.05) was found between iron status and family income for the group of infants (n = 30) from one parent families. Of note, only 7 of these infants were from families with an annual income of > $20,000. The low number of infants in this group limits the ability to predict the true prevalence of IDA and low iron status, or the association with income in the single parent families. No statistically significant association was found between the infants' iron status and the mothers' level of education. A higher prevalence of iron-deficiency anaemia and low iron status was found in infants of mothers born in Canada compared to infants of mothers not born in Canada. The difference was statistically significant (p<0.05) suggesting a higher risk for iron-deficiency anaemia and low iron status among infants' whose mother had been born in Canada. No statistically significant association was found between the infants' iron status and the number of years an immigrant mother had resided in Canada. Ethnic background as reported by the mother was significantly associated (p<0.05) with the iron status of the infants. Specifically, the prevalence of IDA was higher among infants of European and Canadian parentage than among infants of East Indian and Chinese parentage. No statistically significant differences were found between the scores on the visual recognition memory test of the infants with iron-deficiency anaemia, low iron status or normal iron status. In conclusion, the prevalence of iron-deficiency anaemia (6.9%) and low iron status (24.4%) among otherwise healthy 9 month old infants who participated in this study suggests the need to develop strategies for the prevention of iron-deficiency anaemia, or for early detection and treatment. The results of this study show that the infants at highest risk for iron-deficiency anaemia and low iron status in Vancouver, when defined by feeding history, are infants with a history of breast-feeding as the main source of milk for more than 8 months, and infants bottle-fed low iron milk (cows' milk, goat's milk or low iron infant formula). When defined by economic and ethnic background the infants at highest risk for iron-deficiency anaemia are infants of Caucasian mothers (European or Canadian).

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