The Influence of Gender and Age on Prevalence Rates of Comorbid Disorders in Autism

Saturday, May 17, 2014
Atrium Ballroom (Marriott Marquis Atlanta)
K. Supekar, T. P. Iyer, P. Odriozola and V. Menon, Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA

Individuals diagnosed with autism spectrum disorder (ASD) frequently suffer from one or more other disorders. Yet, despite the obvious need to assess the prevalence rates of such comorbidities, few studies have attempted more than a cursory analysis of these across the ASD population.


In this study, we attempt to fill in the gaps in existing studies of ASD comorbidity by examining the influence of gender and age - two important, yet understudied, factors - on ASD comorbidities.


We conduct a comprehensive statistical examination of ten ASD comorbidities including attention deficit hyperactivity disorder (ADHD), autoimmune disorder, bowel disorders, CNS/cranial anomalies, diabetes mellitus, epilepsy, inflammatory bowel disorders, muscular dystrophy, schizophrenia, and sleep disorders by analyzing clinical data of over a million individuals who were patients of the Stanford University Medical Center.


We found significantly higher proportions of ADHD, autoimmune disorders, bowel disorders, CNS/cranial anomalies, epilepsy, and schizophrenia in the ASD population compared to the non-ASD population; illustrating higher susceptibility of individuals on the spectrum to these comorbidities. Critically, there was a lower male bias in comorbidity rates in the ASD than in the non-ASD population; i.e., all ten disorders showed significantly higher prevalence rates in males than females in the non-ASD population whereas the ASD group showed more variation by gender. Additionally, the ASD sample exhibited a more variable trajectory of comorbidity rates with age than did the non-ASD sample.  Epilepsy, for example, decreased from a staggering 41.12% in ages 0-18 down to 24.43% and 15.15% in ages 18-35 and ages 35 and above, respectively; while remaining at a relatively consistent .8 - 1.8% in the non-ASD sample. The observed gender differences varied with age in both groups, but these fluctuations were more dramatic in the ASD population. Notably, the prevalence of bowel disorders was highest in males in both the 0-18 and the 18-35 age range, then switching to higher prevalence in females in ages 35 and above. Similarly, schizophrenia was more prevalent in males 0-18 years of age, but then had higher rates in females in the 18-35 and 35 and above age ranges.


Our results, obtained from comprehensive analyses of one of the largest clinical cohort to date, highlight crucial and unique differences between patterns of comorbidities and their interactions with gender, age, and ASD diagnosis. These findings may prove to be instrumental in developing more efficient gender- and age- appropriate diagnostic and treatment strategies for ASD and related disorders. More generally, our study highlights the importance of understanding and accurately identifying patterns of comorbidity in the ever-growing ASD population as these co-occurring problems mediate the degree of adaptation, lifestyle, and prognosis of individuals on the spectrum.