72 Prevalence of Neurodevelopmental Disorder among Indigenous Children: A Systematic Review

Abstract Background Neurodevelopment involves sensory-motor, cognitive, and social-emotional domains, which can be influenced by biological and psychosocial factors. Poor neurodevelopment can result in missing developmental milestones and neurodevelopmental disorders (NDs) that translate into negative consequences for long-term health and well-being. Indigenous children in countries with similar colonial histories face a disproportionate burden of infant mortality, chronic diseases, injuries, and disability compared to non-Indigenous children. However, there is no consensus on the prevalence of NDs among Indigenous children around the world. Objectives This systematic review (PROSPERO 2021 CRD42021238669) synthesized current evidence on the prevalence of NDs among Indigenous children in Australia, Canada, New Zealand, and the USA. Design/Methods Comprehensive searches of five databases from 2005 to Feb 15, 2021 were conducted to identify cohort and cross-sectional studies that assessed the objective. Two independent reviewers conducted study selection, data extraction/analysis, and risk of bias assessment. Risk of bias was assessed using the Newcastle-Ottawa scale for cohort and ecological studies (adapted), and the Quality Assessment Tool for Prevalence Studies by Hoy et al. for cross-sectional studies. Prevalence odds ratios (pOR) with 95% confidence intervals (CI) were calculated in random-effects meta-analyses for each ND outcome if there were two or more studies of the same study design. Results Of the 864 studies identified, 25 studies met the inclusion criteria. Twelve studies were conducted in Australia, one in Canada, four in New Zealand, and eight in the USA. Four studies evaluated attention-deficit/hyperactivity disorder (ADHD) prevalence, 13 for autism spectrum disorder (ASD), 10 for intellectual disability (ID), and five for motor disorders (MD). Most cohort studies (10/17) had high risk of bias. All cross-sectional studies (n=8) had low risk of bias. The prevalence of ADHD, ASD, ID, and MD for Indigenous children ranged from 2.7-3.9%, 0.07-3.0%, 1.1-3.9%, and 0.18-0.47%, respectively. Prevalence in non-Indigenous children ranged from 1.6-5.6%, 0.31-3.3%, 0.87-2.3%, and 0.22-0.37%. In cross-sectional studies, Indigenous children had decreased odds of ASD (three studies; pOR=0.80; 95% CI: 0.71-0.89) compared to non-Indigenous children. In cohort studies, higher odds of MD (two studies; pOR=1.57; 95%CI: 1.35-1.84) and lower odds of ASD (four studies; pOR=0.46; 95% CI: 0.28-0.76) were found in Indigenous children compared to non-Indigenous children. Conclusion Prevalence rates are greater in Indigenous children for MD and lower for ASD compared to their non-Indigenous counterparts. Differences in NDs prevalence between Indigenous and non-Indigenous children may be due to differences in access to health care services/assessment.