The Impact of Age on Income-Related Health Status Inequalities from Birth to Adolescence: A Systematic Review with Cross-Country Comparisons

Abstract

To examine the effect of age on associations between household income and overall health from birth to adolescence, and whether age patterns vary by country. It is uncertain whether income-related health inequalities remain stable, widen, or narrow as children age, which impacts optimal timing of equity-focused interventions. Systematic review (CRD42016038583) of MEDLINE, Embase, PsycINFO, CINAHL, SocINDEX (full-text), and EconLit (full-text) to April 2017. We included observational studies and trials in children and adolescents (0-18 years of age), examining age differences in associations between income and overall health (self-rated, clinician-rated, proxy-rated). One reviewer extracted data; 2 evaluated risk of bias. Thirty-eight articles containing 43 studies (30 cross-sectional, 13 cohort) were identified, from high-income (n = 39) and middle-income (n = 4) countries. In the US (n = 21), positive income-health associations emerged in early childhood, and these inequalities typically widened progressively into adolescence. Relative to 0- to 3-year-olds, ratios of income-health coefficients ranged from 1.10-3.71 for 4-8 years of age, 1.26-3.86 for 9-12 years of age, 1.36-6.71 for 13-17 years. In the United Kingdom and Ireland (n = 8), inequalities emerged in early-to-mid childhood, but age patterns were less consistent. In other high-income countries (Australia, Canada, France, Germany, Japan, Republic of Korea), inequalities mostly persisted or widened with age. In middle-income countries, inequalities appeared to narrow (Indonesia n = 2) or persist (Brazil n = 2) with age. Limitations are unclear/high risk of bias and dataset overlap for some studies. In many countries, income-related health status inequalities persist or widen as children age. Interventions that improve health equity early in the life-course are needed.