Abstract
The associations between autism spectrum disorder (ASD) and physical diseases (PD) based on ICD-8 and ICD-10 diagnoses were studied, comparing with the risks of the general population. All individuals diagnosed before 30th April 2018 with ASD (n = 12,063) and a 5% random sample of the general population (n = 41,251) were drawn from Danish registers of the birth cohorts 1984-1995. For each of the entire spectrum of 13 PD categories, participants were followed from birth to first diagnosis, death, emigration, or 31st December 2017, whichever came first. Time from inclusion at birth to time of first physical diagnosis, accounting for censoring, was studied by use of time-stratified Cox models. When compared to the control sample, the individuals with ASD had a substantial added immediate risk in infancy and in childhood for 12 of the 13 categories. Particularly prominent were estimated associations for nervous system diseases at ages 0-9, and diseases of the eye and adnexa at ages 0-11. The associations were observed for both sexes, but were stronger among females than males, especially for genitourinary system diseases. On the cumulative scale, individuals with ASD were at pronounced greater risk through follow-up for 8 categories, with the greatest cumulative risk of respiratory system diseases, which at ages 5 and 30 was 24.9% and 41.5% for the ASD cohort while for the control sample it was 16.3% and 34.5% at the same ages. Especially in infancy and childhood, the present study found increased risks for a multitude of physical diseases.