A Study on the Incidence and Comorbidities of Autism Spectrum Disorders Accompanied by Intellectual Disabilities in Yonago City, Japan

Abstract

Autism spectrum disorders (ASD) with intellectual disabilities may be associated with many factors. This study focused on patients with ASD with intellectual disabilities, defined by a threshold intelligence quotient (IQ) or development quotient (DQ) of 70. We also discuss comorbidities and other factors related to ASD. We extracted case records of patients born between April 1995 and March 2001 who lived in Yonago City, as of January 2011, and had visited the two specialist institutions for consultation regarding developmental issues. The list was further narrowed down to patients identified, as having ASD by pediatric neurologists based on Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) (DSM-5). We selected patients with < IQ/DQ 70 using the most recent intelligence/development test to determine comorbidities and other factors related to ASD. The data of 81 patients (59 males and 22 females) were extracted, corresponding to an incidence of 76.2 patients out of every 10,000 births. The male-to-female ratio was 2.7:1. Comorbidities and related factors of ASD were observed in 25 cases (30.9%). Eleven cases had perinatal abnormalities. Other abnormalities were observed in 17 cases, including epilepsies in 7, chromosomal abnormalities in 4, familial mental retardation in 1, and acquired brain injury in 1. It is important to treat and support individuals with ASD and intellectual disabilities taking into account the characteristics and prognosis of the comorbidities and related factors.