Prevalence of intellectual disability: a meta-analysis of population-based studies.
Roughly a large share of the world has ID, with higher counts in low-income nations and among kids.
01Research in Context
What this study did
The team pooled 52 population studies from every continent. They counted people with intellectual disability in the general public, not just clinics.
They split results by country income, age group, and how ID was measured. This gives one global snapshot instead of many local guesses.
What they found
About 1 in every 100 people has ID worldwide. Poorer countries show higher rates, up to 1.5 in 100.
Children appear more often than adults, partly because school screening catches them early.
How this fits with other research
Nuebling et al. (2024) used the same head-count to show sleep problems are common in this group. Their meta-analysis sits on top of Leung et al. (2011) like a second story.
Dudley et al. (2019) warn U.S. health surveys miss many adults with IDD. The a large share figure looks smaller in American data sets, but that is a counting flaw, not a real gap.
Petrovic et al. (2016) zoom inside facilities and find a large share of inpatients have metabolic syndrome. K et al. tells us how big the waiting room is; B et al. shows half of those inside carry extra cardio risk.
Why it matters
When you plan services, budget for at least a large share of your catchment area. In a city of 500 000, expect 5 000 clients with ID. Use the higher child rate to justify school-based slots and the adult rate to size day-program seats. Pair these numbers with Petrovic et al. (2016) to flag cardio screening for roughly half of your adult caseload.
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02At a glance
03Original abstract
Intellectual disability is an extremely stigmatizing condition and involves utilization of large public health resources, but most data about its burden is based on studies conducted in developed countries. The aim of this meta-analysis was to collate data from published literature and estimate the prevalence of intellectual disability across all such studies. The review includes studies published between 1980 and 2009, and includes data from populations that provided an overall estimate of the prevalence of intellectual disability. Meta-analysis was done using random effects to account for heterogeneity. Sub-group analyses were also done. The prevalence of intellectual disability across all 52 studies included in the meta-analysis was 10.37/1000 population. The estimates varied according to income group of the country of origin, the age-group of the study population, and study design. The highest rates were seen in countries from low- and middle income countries. Studies based on identification of cases by using psychological assessments or scales showed higher prevalence compared to those using standard diagnostic systems and disability instruments. Prevalence was higher among studies based on children/adolescents, compared to those on adults. Higher prevalence in low and middle income group countries is of concern given the limitations in available resources in such countries to manage intellectual disability. The importance of using standardized diagnostic systems to correctly estimate the burden is underlined. The public health and research implications of this meta-analysis have been discussed.
Research in developmental disabilities, 2011 · doi:10.1016/j.ridd.2010.12.018