Significant cognitive delay among 3-to 4-year old children in low-and middle-income countries: prevalence estimates and potential impact of preventative interventions

Background: We sought to: (i) estimate the prevalence of significant cognitive delay (a marked delay in the development of general cognitive functioning) among nationally representative samples of young children in middle-and low-income countries; (ii) estimate the total number of children under 5 years of age with significant cognitive delay living in low-and middle-income countries; and (iii) estimate the potential impact of five preventative interventions. Methods: Secondary analysis of data collected in Rounds 4 and 5 of UNICEF's Multiple Cluster Indicators Surveys in 51 countries involving 163 293 3-to 4-year-old children. Adjusted population-attributable fractions were used to estimate the potential impact of five interventions based on Sustainable Development Goals (SDGs). Results: The prevalence of significant cognitive delay in 3-to 4-year-old children in middle-and low-income countries was 10.1% (95% confidence interval 9.7-10.4%). Prevalence was strongly inversely related to country economic wealth. The estimated total number of children under 5 with significant cognitive delay living in low-and middleincome countries was just under 55 million. This number could be reduced by over 60% if three separate SDGs were achieved; every mother had secondary-level education, every household had access to improved water and sanitation, and every child had an acceptable level of home stimulation. Conclusions: Our results provide additional evidence in support of a range of specific preventative interventions in early childhood to reduce the loss of developmental potential among children in low-and middle-income countries.