Parental Age and the Risk of Autism Spectrum Disorder in Oman

Objective: This study aimed at evaluating advanced parental age as a risk factor for Autism Spectrum Disorder (ASD) in an Omani cohort. Methods: Case-control study of 278 ASD cases compared with 722 sex-matched controls retrieved from the electronic records of the Developmental Paediatric Clinic, Sultan Qaboos University Hospital (SQUH) between January 2015 and June 2016. Results: ASD cases (76.6% male) were mostly diagnosed between 3-4 years of age, with more than 50% of them originating from Muscat and Batinah governorates. Compared to controls, mothers from the case group had significantly higher educational level (post-secondary education versus high school/no formal education (odds-ratio (OR)=1.62; 95% C.I. 1.20-2.19). In a multivariate logistic regression, the odds ratio of maternal age as a risk for ASD increased dramatically with advancing age category (using age<25 as a reference, OR was 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 referent, OR was 2.20, 2.36, and 3.12 for age categories 30-34, 35-39 and 40-44 years); however, there was a drop in the effect with paternal age ≥ 45 years (OR=1.42; 95% C.I .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. Keywords: Autism; parental age; case-control study