The Influence of Gender and Age on Prevalence Rates of Comorbid Disorders in Autism
Background: 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.Objectives:
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.
Further Readings of Interest
Co-Morbidities of Epilepsy
The association with epilepsy was the strongest for
cognitive dysfunction (OR=28.1; 95% CI=23.3-33.8);
autism spectrum disorders (OR=22.2; 95% CI=16.8-29.3);
intellectual disability (OR=12.9; 95% CI=11.6-14.3); and
stroke (OR=4.2; 95% CI=4.1-4.4).
Co-Morbid Clusters in Autism
Four subgroups were identified.
The first was characterized by seizures (n = 120, subgroup prevalence 77.5%).
The second (n = 197) was characterized by multisystem disorders including gastrointestinal disorders (prevalence 24.3%) and auditory disorders and infections (prevalence 87.8%),
and the third was characterized by psychiatric disorders (n = 212, prevalence 33.0%).
The last group (n = 4316) could not be further resolved.
The prevalence of psychiatric disorders was uncorrelated with seizure activity (P = .17), but a significant correlation existed between gastrointestinal disorders and seizures (P < .001).
Co-morbid Conditions and Autism – Harvard Medical
An important research paper has just been released by researchers at Harvard Medical School in which they examine the co-morbid conditions associated with autism. Over 14,000 individuals under 35 were examined and the following prevalence figures drawn.
“19.44% of ASD patients had epilepsy as compared to 2.19% in the overall hospital population (95% confidence interval for difference in percentages 13.58-14.69%), 2.43% of ASD with schizophrenia vs. 0.24% in the hospital population (95% CI 1.89-2.39%), inflammatory bowel disease (IBD) 0.83% vs. 0.54% (95% CI 0.13-0.43%), bowel disorders (without IBD) 11.74% vs. 4.5% (95% CI 5.72-6.68%), CNS/cranial anomalies 12.45% vs. 1.19% (95% CI 9.41-10.38%), diabetes mellitus type I (DM1) 0.79% vs. 0.34% (95% CI 0.3-0.6%), muscular dystrophy 0.47% vs 0.05% (95% CI 0.26-0.49%), sleep disorders 1.12% vs. 0.14% (95% CI 0.79-1.14%).”
Epilepsy – 19.4%
Schizophrenia – 2.43%
Inflammatory Bowel Disease – .83%
Bowel Disorders – 11.74%
CNS / Cranial abnormalities 12.45%
Diabetes mellitus type I – .79%
Muscular Dystrophy .47%
Sleep Disorders 1.12%
Additionally in the published figures …
“Autoimmune disorders (excluding DM1 and IBD) were not significantly different at 0.67% vs. 0.68% (95% CI -0.14-0.13%).”
…and what may be of a primary concern.
“Three of the studied comorbidities increased significantly when comparing ages 0-17 vs 18-34 with p<0.001: Schizophrenia (1.43% vs. 8.76%), diabetes mellitus type I (0.67% vs. 2.08%), IBD (0.68% vs. 1.99%) whereas sleeping disorders, bowel disorders (without IBD) and epilepsy did not change significantly.”