Measuring Child Socio-Economic Position in Birth Cohort Research: The Development of a Novel Standardized Household Income Indicator

Abstract

The assessment of early life socioeconomic position (SEP) is essential to the tackling of social inequalities in health. Although different indicators capture different SEP dimensions, maternal education is often used as the only indicator in birth cohort research, especially in multi-cohort analyses. Household income, as a direct measure of material resources, is one of the most important indicators, but one that is underused because it is difficult to measure through questionnaires. We propose a method to construct a standardized, cross-cohort comparable income indicator, the “Equivalized Household Income Indicator (EHII)”, which measures the equivalized disposable household income, using external data from the pan-European Union Statistics on Income and Living Conditions (EUSILC) surveys, and data from the cohorts. We apply this method to four studies, Piccolipiù and NINFEA from Italy and ELFE and EDEN from France, comparing the distribution of EHII with other SEP-related variables available in the cohorts, and estimating the association between EHII and child body mass index (BMI). We found that basic parental and household characteristics may be used, with a fairly good performance, to predict the household income. We observed a strong correlation between EHII and both the self-reported income, whenever available, and other individual socioeconomic-related variables, and an inverse association with child BMI. EHII could contribute to improving research on social inequalities in health, in particular in the context of European birth cohort collaborative studies.

The LifeCycle Project-EU Child Cohort Network: a federated analysis infrastructure and harmonized data of more than 250,000 children and parents

“…Based on the primary research focus in the LifeCycle Project, a priority list of variables has been developed for harmonisation. The cohort studies participating in the EU Child Cohort Network will be further enriched with novel harmonized integrated data on early-life stressors related to socio-economic, migration, urban environment and lifestyle determinants, based on data availability within the cohorts and external data from registries [ 36 ]. Integrated data will also be used to construct a novel holistic ‘dynamic early-life exposome’ model, which will encompass many human environmental exposures during various stages of early life [ 37 – 40 ].…”

Determination of saliva epigenetic age in infancy, and its association with parental socio-economic characteristics and pregnancy outcomes

“…The equivalised total disposable household income indicator at birth has been developed within the European Horizon 2020 LifeCycle project and it uses external data from the pan-European surveys 'European Union Statistics on Income and Living Conditions' (EUSILC) and internal household and parental characteristics available within cohorts. 38 For the NINFEA cohort, the income indicator has been constructed using the following parental and household baseline characteristics: cohabitation with partner, family size (number of children and adults in the household), dwelling type, number of rooms in the house, maternal age and country of birth, parental education and occupation and maternal job coded using the ISCO-88 (International Standard Classification of Occupations) classification. 38 Pregnancy outcomes included birthweight (grams), gestational age (weeks), size for gestational age (small, appropriate and large for gestational age, based on the 10th and the 90th percentile of the World Health Organization birthweight for sex and gestational age charts) 39 and mode of delivery (vaginal delivery vs. caesarean section).…”

Population-Based Birth Cohort Studies in Epidemiology

“…Two papers addressed the topic of indicators of socioeconomic disadvantage [ 10 , 13 ]. Evidence suggests that socioeconomic disadvantages in early-life can affect child health and have long-term effects also on adult health [ 14 , 15 ].…”

“…However, each single indicator captures different, likely correlated, dimensions of the child’s SES. As Pizzi and colleagues stated, the household’s disposable income is potentially one of the most important single indicators of the child’s SES, but it is underused because it is difficult to measure through questionnaires [ 13 ]. Moreover, comparing income across populations and studies might be complex, as different studies might collect different types of income and at different points in time.…”

“…The authors therefore proposed a method for constructing a standardized and comparable cohort-specific household income indicator (“Equivalized Household Income Indicator (EHII)) for child SES to be used in European birth cohort studies, using external data from the pan-European surveys “European Union Statistics on Income and Living Conditions” (EUSILC) and internal data from four Italian and French birth cohorts. Being based on external data from the EUSILC surveys, which are conducted in several European countries using the same design and procedures, the EHII allows researchers to obtain a harmonized family income measure over different European populations, that can be used in the context of European collaborative studies [ 13 ].…”