Prevalence of intellectual disability among eight-year-old children from selected communities in the United States, 2014.
Mary E Patrick, Kelly A Shaw, Patricia M Dietz and 10 others
PMID 33272883WHAT IT FOUND
Intellectual disability affected 11.8 of every 1,000 eight-year-olds in nine US states.
Prevalence was twice as high in boys as girls and highest in Black children. Rates dropped as neighborhood income and education rose. Children in lower-income areas were tested later.
Key findings
01The overall prevalence of intellectual disability was 11.8 per 1,000 children, ranging from 8.0 per 1,000 in Minnesota and Tennessee to 16.1 per 1,000 in Arkansas.
02Prevalence was 15.8 per 1,000 among males and 7.7 per 1,000 among females, with the highest rates among Black and Hispanic males and the lowest among White females.
03Intellectual disability prevalence was inversely associated with socioeconomic status, dropping from 16.1 per 1,000 in the lowest income tertile to 7.4 per 1,000 in the highest.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
The study definition for intellectual disability did not require adaptive functioning scores, which are part of other clinical definitions, though a sensitivity analysis showed overall patterns remained unchanged. Data sources typically excluded private or home-schooled students, which may lead to an underestimation of prevalence. The participating sites are not representative of the entire United States, so results should not be extrapolated nationally. Socioeconomic status denominators assumed equal distribution of children aged 5-9, which may not hold true in all areas.
Declared interests
The authors declared no potential conflicts of interest. The study was supported by the U.S. Government, P.H.S.
The easy way to misread this
Do not assume that higher prevalence rates in specific racial or socioeconomic groups indicate a biological difference. The study attributes these disparities to environmental factors, access to healthcare, and differential referral patterns for testing rather than inherent traits.