Revisiting the Prevalence of Autism Spectrum Disorder among Omani Children: A multicentre study

Objectives: This study aimed at evaluating advanced parental age as a risk factor for autism spectrum disorder (ASD) in an Omani cohort. Methods: This case-control study compared 278 ASD cases with 722 gender-matched controls, retrieved from the electronic records of the Developmental Paediatric Clinic, Sultan Qaboos University Hospital, Muscat, Oman, between January 2015 and June 2016. Results: Most ASD cases were male (76.6%) and mostly diagnosed between 3–4 years of age, with more than 50% of the cases originating from Muscat and Batinah governorates. Compared to controls, mothers from the case group had significantly higher educational levels (post-secondary education versus high school/no formal education: odds ratio [OR] = 1.62, 95% confidence interval [CI]: 1.197–2.192). In a multivariate logistic regression, the OR of maternal age as a risk for ASD increased dramatically with advancing age category (using age <25 as reference, OR = 3.39, 6.12, 7.86 and 13.13 for age categories 25–29, 30–34, 35–39 and ≥40 years, respectively). The ORs of advancing paternal age as a risk for ASD were also statistically significant (using age <30 as reference, OR = 2.20, 2.36 and 3.12 for age categories 30–34, 35–39 and 40–44 years, respectively); however, there was a drop in the effect with paternal age ≥45 years (OR = 1.42; 95% CI: 0.64–3.15). Conclusion: Both maternal and paternal increased age were associated with a higher risk of ASD; however, the association was more pronounced and more consistent with advanced maternal age compared to paternal age.

Objectives: This study aimed to explore the intelligence quotient (IQ) profile among children with autism spectrum disorder (ASD) and identify the most important subscales that predict the IQ. The analysis of an intellectual profile with age and gender differentials and the identification of a battery of subscales of intelligence are important for clinical management of ASD among children and for facilitating placement for remedial and educational services. Methods: Data were collected through an exploratory study of 100 children aged between three and 13 years, who were referred to the department of child health and development in Sultan Qaboos University Hospital, a tertiary hospital, in Oman between June 2016 and June 2019. Results: Among the 100 participants of this study, 79% were male, resulting in a male–female ratio of 4:1. The mean of full-scale IQ was found to be 68.6 ± 18.1. Furthermore, the mean of nonverbal IQ (73.5 ± 17.5) was significantly higher than that of verbal IQ (65.5 ± 17.6). Finally, more than half (61%) of the children were observed to have had mild to moderate impairment in their IQ levels. Conclusions: Age and gender showed no significant association with IQ level. The regression analysis identified nonverbal fluid reasoning, nonverbal visual-spatial processing, nonverbal working memory and verbal knowledge as the significant predictors of total IQ. The crucial dimensions of verbal and nonverbal IQ identified in this study can be used to evaluate complicated cases.

Deficits in social communication, restricted interests, and repetitive behaviours are hallmarks of autism spectrum disorder (ASD). Despite high genetic heritability, the majority of clinically diagnosed ASD cases have unknown genetic origins. We performed genome sequencing on mothers, fathers, and affected individuals from 104 families with ASD in Oman, a Middle Eastern country underrepresented in international genetic studies. This approach identified 48 novel candidate genes significantly associated with ASD in Oman. In particular, 35 of these genes have been previously implicated in neurodevelopmental disorders (NDDs) in other populations, underscoring the conserved genetic basis of ASD across ethnicities. Genetic variants within these candidate genes that would impact the encoded protein included 1 insertion, 4 frameshift, 6 splicing, 12 nonsense, and 67 missense changes. Notably, 61% of the SNVs were homozygous, suggesting a prominent recessive genetic architecture for ASD in this unique population. The scarcity of genetic studies on ASD in the Arabian Peninsula has impeded the understanding of the unique genetic landscape of ASD in this region. These findings help bridge this knowledge gap and provide valuable insights into the complex genetic basis of ASD in Oman.