Fig. 1.

Flow diagram of analytic sample inclusion and exclusion. Analytic sample inclusion was stratified by poverty exposure.

Of the 73 493 children who were present at birth in the dataset, 5695 (7.8%) were lost to follow-up by age 5 based upon registration in Medical Services Plan (MSP) health insurance records from age 0 to age 5. Children who were lost to follow-up did not differ significantly by sex, but were more likely to have been receiving MSP subsidy at age 0, be living in the lowest income quintile neighbourhood at age 0, to be a second-generation immigrant, and on average had mothers who were younger at child birth in comparison to children who were not lost to follow-up. 15 369 participants were present in B.C. from ages 0 to age 5 and not lost to follow-up, and had successful linkages to administrative data records and a completed Early Development Instrument (EDI) survey. 397 (2.6%) of these 15 369 participants had missing EDI outcome data. Missingness in individual EDI domain scales did not appear to differ significantly between one another, and each had a missingness between 1.0% and 1.7%. 179 children (1.2%) had both household poverty and neighbourhood poverty but in different years between age 0 to 2 (not concurrent/combined household and neighbourhood poverty), and therefore were not categorized into one of the four poverty exposure groups. For children who were present in B.C. during the study period with successful data records linkages, the administrative data variables (immigrant generation status, birthweight adjusted for gestational period, mother marital status, mother age at birth category) had ≤1% missing data.