Sex differences in 5‐year incidence and prevalence of physical illnesses following early childhood autism diagnosis

Abstract Background Sex differences in the clinical presentation of autism are established, but evidence on early‐life co‐occurring physical illnesses in early‐diagnosed autistic individuals is scarce. This nationwide cohort study examined sex‐stratified incidence of physical illnesses within 5 years after autism spectrum disorder (ASD) diagnosis in children ≤5 years. Methods Using Taiwan's National Health Insurance Research Database (2000–2019), we identified 36,656 autistic males and 9024 autistic females newly diagnosed before age 6 and followed for five years. Adjusted odds ratios and hazard ratios for physical illnesses were estimated via multivariate logistic and Cox regression, controlling for demographic, clinical, and healthcare utilization factors. Analyses were stratified by intellectual disability status. Results Within 5 years following an ASD diagnosis, autistic females exhibited higher incidences of cardiovascular diseases, cerebrovascular diseases, epilepsy, and irritable bowel syndrome, with generally modest to moderate effect sizes (approximately 1.3–2.3). In contrast, autistic males consistently demonstrated a higher risk of asthma. Prevalence analyses revealed similar patterns. Stratified analyses further indicated that, among children without intellectual disabilities, autistic females remained at elevated risks for cardiovascular diseases and epilepsy, with effect sizes ranging from approximately 1.44 to 2.86. Additional increased risks of hyperlipidemia and atopic dermatitis were also observed in autistic females, whereas autistic males continued to show higher risks of asthma and diabetes mellitus. Conclusion Autistic females in early childhood face greater cardiometabolic and neurological burdens, while males are more prone to respiratory and metabolic conditions. These sex‐ and cognition‐specific risk profiles support tailored screening—cardiovascular/metabolic monitoring for females and respiratory disease prevention for males—to inform clinical care and health policy.