Parental Age and the Risk of Autism Spectrum Disorder in Oman: A case-control 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.