Massive inequalities in the distribution of wealth, both between and within countries, are a key challenge to sustainable development.1 Despite progress in the alleviation of poverty in most parts of the world over the past three decades, wealth inequalities still exist, and several low-income countries have seen the incomes of the bottom 40% stagnating, or even decreasing.2, 3 In a time trend analysis of 83 countries, the global average Gini index—weighted by national population size—increased from 36·7 in 2000 to 40·8 in 2015. This finding indicates that the average person was living in a country where inequality was on the rise.4
Addressing inequality is at the core of the Sustainable Development Goals5 target of leaving no one behind.6 Economic inequality is not only important per se, but it is also a major driver of health status, as is emphasised by initiatives aimed at tackling the social determinants of health.7 In addition to how the poorest communities are at increased risk of illness and malnutrition, inequality affects the health of entire populations. Social gradients in health are ubiquitous, with stepwise increases in illness and mortality down the socioeconomic spectrum.8
There is ample literature on the effect of poverty during the life course in high-income societies. Birth cohort analyses, from countries such as the UK, New Zealand, USA, and Norway, point to the lifelong effects of material and psychosocial exposures on health and human capital.9 By contrast, the literature from low-income and middle-income countries (LMICs) on such topics is scarce. Nevertheless, many (if not most) children currently living in LMICs experience suboptimal nurturing care,10, 11 an innovative concept that encompasses child health, nutrition, learning, relationships, security, and safety. These five components of nurturing care are largely determined by poverty; a “cause of the causes”12 of poor health and development. Exposure to adversity in early life,9, 13 for which poverty is a proxy measure, is postulated to be a major driver of adequate nurturing care and of its consequences on human capital.
Key messages
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Data from low-income and middle-income countries (LMICs) substantiate the negative effects of early-life poverty on the survival, nutrition, and cognitive development of children and adolescents
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Analyses of long-term birth cohorts in LMICs show that early-life poverty is strongly and inversely associated with human capital indicators, such as adult height, achieved schooling, and intelligence
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By contrast, some risk factors for non-communicable diseases, including overweight and signs of metabolic syndrome in adults, are less common in men, but not in women, exposed to early-life poverty than in the rest of the population
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Broad and multisectoral anti-poverty policies and programmes need to be urgently strengthened to offset the impact of COVID-19 on poverty and to promote the health and development of children and adolescents, both in the short term and long term
The first paper in this Series used evidence from longitudinal studies to consider conditions of survival, growth, disability, and education in world regions and their effects on crucial periods in the lifecycle before adulthood that build the foundation for human capital.11 In this second Series paper, we review data on key conditions related to human capital in children, adolescents, and adults, and analyse how early-life poverty contributes to their enduring prevalence throughout the life course. Using data from 95 national surveys in LMICs, we assess the presence and magnitude of social gradients in the health, nutrition, and cognitive development of children and adolescents, reflecting the accrual of human capital. Additionally, we use data from six large, long-running birth cohorts in LMICs to explore the long-term associations between early-life poverty and health and human capital outcomes in adulthood. In both sets of analyses, we use indicators related to the constructs of nurturing care and of human capital, including survival, health, nutrition, and cognition. We also report on selected conditions that affect an individual's ability to contribute to society, including stunted height14 and obesity15 in adulthood, teenage motherhood,16 and psychological symptoms.17 This information informs consideration of interventions, intersectoral approaches, and policies, which are addressed in the third18 and fourth19 papers of this Series.