The prevalence of significant cognitive delay among 3- to 4-year-old children growing up in low- and middle-income countries: results from 126 nationally representative surveys undertaken in 73 countries.
One in ten preschoolers in low- and middle-income countries has serious cognitive delay, and poverty plus low maternal education are the clearest red flags.
01Research in Context
What this study did
Emerson et al. (2023) looked at 126 national surveys from 73 low- and middle-income countries. They asked one simple question: how many 3- to 4-year-olds show serious cognitive delay?
The team used the same test in every country so the numbers could be compared. They also checked if poverty, mom’s schooling, or country wealth changed the risk.
What they found
About one in every ten preschoolers scored in the serious delay range. The poorest kids with the least-educated moms faced the highest risk.
National wealth mattered too. Kids in the poorest countries were more likely to show delay than kids in better-off countries.
How this fits with other research
Camargos et al. (2016) saw lower Bayley cognitive scores in overweight infants. E et al. find weight is not the big risk at preschool age; poverty and mom’s schooling are. The difference is age: infant body fat may matter more when the brain is just starting out.
Howe et al. (2016) also showed mom’s education predicts 5-year IQ in very-low-birth-weight toddlers. E et al. widen the lens: the same link holds across an entire global sample, not just sick babies.
Dzanko et al. (2026) give the next step. They show just 3 hours a week of low-intensity developmental-behavioral therapy plus parent tips can move the needle for preschoolers with delay in the same low-resource settings E et al. mapped.
Why it matters
If you work in low-resource areas, expect one child per table to need extra cognitive support. Screen with simple tools, then act fast: brief parent coaching and low-dose ABA can fit tight budgets and still yield gains. Track mom’s schooling and household income to spot the highest-risk kids first.
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02At a glance
03Original abstract
BACKGROUND: We sought to (1) update estimates of the prevalence of significant cognitive delay (SCD) among nationally representative samples of young children overall, and in upper-middle, lower-middle and low-income countries; (2) investigate whether variation in prevalence between countries was systematically associated with national wealth and other country characteristics; (3) investigate the stability of prevalence estimates over time; (4) examine the correlation between SCD and 2019 Global Burden of Disease estimates on the prevalence of the impairment of developmental intellectual disability under 5 years of age; and (5) investigate the extent to which risk of SCD within countries varies with child age and gender, maternal education and household wealth. METHODS: Secondary analysis of data collected in 126 nationally representative Multiple Cluster Indicators Surveys (MICS) conducted under the supervision of UNICEF in 73 countries involving a total of 396 596 3- to 4-year-old children. RESULTS: The overall prevalence of SCD was 9.7% (95% CI 8.6-10.9%). Between-country variation in prevalence was strongly related to national wealth, the Human Development Index, the Human Inequality-adjusted Development Index and the Multidimensional Poverty Index, but not income inequality. In the 46 countries in which more than one survey was available prevalence estimates were reasonably stable over time (r = 0.80, P < 0.001). There were strong independent associations between increased risk of cognitive delay and younger child age, lower levels of maternal education and lower levels of household wealth (but not male gender). There was only a weak association across countries between the estimated prevalence of SCD and Global Burden of Disease estimates of the under 5 prevalence of the impairment of developmental intellectual disability. CONCLUSIONS: UNICEF's MICS data are readily (and freely) available to researchers and provide a cost-effective opportunity for researchers who are concerned about better understanding the situation of young children growing up in the world's LMICs with a marked loss of developmental potential in areas of cognition and learning.
Journal of intellectual disability research : JIDR, 2023 · doi:10.1111/jir.12976