Population prevalence and risk factors for iron deficiency in Auckland, New Zealand.
Previous prevalence estimates of iron deficiency (ID) in young New Zealand children are inaccurate because of sampling bias and imprecise definition of ID. The aim of this study was to estimate the prevalence of ID in children aged 6-23 months and the factors associated with ID. An ethnically stratified sample identified from random residential address start points. Children resident in Auckland, New Zealand were enrolled from 1999 to 2002. Children with elevated C-reactive protein (>4 mg/L) were excluded. Iron status was determined in 324 (78%) of 416 enrolled children. Analyses adjusted for clustering and weighted for ethnic stratification. ID defined as abnormal values for two or more of serum ferritin (<10 microg/L), iron saturation (<10%) and mean cell volume (<73 fl). ID was present in 14% (95% confidence interval (CI) 9-17%). ID prevalence varied with ethnicity (Maori 20%, Pacific 17%, other 27%, New Zealand European 7%, P = 0.005), but not with social deprivation. In a multivariate analysis that adjusted for low birthweight, there was an increased risk of ID associated with a body mass index >or= 18.5 kg/m(2) (RR = 4.34, 95% CI 1.08-10.67), and with receiving no infant or follow on formula (RR = 3.60, 95% CI 1.56-6.49). ID is prevalent in young New Zealand children. Variance in ID prevalence with ethnicity but not social deprivation implies that cultural practices influence iron status. Young children with more rapid growth are at increased risk of ID as are those receiving milk other than that specifically modified for them.