Trends in the prevalence of intellectual disability among children in Taiwan.

Abstract

Intellectual disability (ID) is a major developmental disability. However, data on changes in the prevalence over time at the national level are limited. Using data from the national disability registry, we conducted an ecological study to evaluate the time trends of ID among children in Taiwan. We calculated the prevalence of ID by age, sex and severity, from 2000 to 2011, and assessed the time trends. During the study period, the overall prevalence of ID in children aged 3-17years increased from 3.60 to 5.91 per 1000 (β=0.22, P<0.001, r2 =0.97). The prevalence of mild ID (MID, intelligence quotient: 50-69) increased from 1.30 to 3.60 per 1000 (β=0.21, P<0.001, r2 =0.98). However, the prevalence of severe ID (SID, intelligence quotient: <50) was relatively constant, between 2.22 and 2.38 per 1000 (β=0.01, P=0.076, r2 =0.96). Boys had a higher prevalence than girls, and the average boy-to-girl prevalence ratio was 1.42 for MID and 1.31 for SID. The boy-to-girl prevalence ratios of MID and SID decreased over time (β=-0.01, P<0.001, r2 =0.99 for MID; β=-0.01, P<0.001, r2 =1.00 for SID). The prevalence of ID in Taiwanese children increased from 2000 to 2011 and was largely attributable to increases in MID. Boys had a higher prevalence of ID and were more likely to have MID.