Medical Conditions and Health Care Utilization Associated with ASD in Adulthood

Background:  Children with autism spectrum disorder (ASD) are growing up and becoming adults. However, very little is known about medical conditions and health care utilization patterns among this growing population.  Elucidation of these medical care issues is critical to the development of effective strategies for health care delivery to adults with ASD.

Objectives:  The objectives of this study are: 1) to describe the prevalence of ASD in adults, 2) to investigate the frequency of medical and psychiatric co-morbidities and utilization of psychotropic and other medications, 3) to describe utilization of health services among adults with ASD, and 4) to assess adult medicine and other practitioners’ knowledge about ASD.

Methods:  The study population was drawn from the total population of adult members of Kaiser Permanente Northern California (KPNC) as of 2012 (N~2.4 million).  We utilized data routinely captured in KPNC electronic clinical databases for all analyses.  ASD cases were defined according to International Classification of Diseases-9-Clinical Modification (ICD-9-CM) 299.0; Asperger’s Disorder or Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS) (ICD-9-CM 299.8).  Adults without an ASD diagnosis were sampled at a 10:1 ratio and constituted the comparison group.  We calculated overall prevalence of ASD, and prevalence by sex, age group (18-24, 25-29, 30-34, 35-39, 40-44, 45-49, 50-54, 55-59, 60-64, 65+), and race/ethnicity (white, Hispanic, African American, Asian, Other). We also calculated the prevalence of psychiatric and medical co-morbidities, and quantified the utilization of primary care, specialty care, and preventive care services overall and by sex, age group, and race/ethnicity. Specific psychiatric and medical co-morbidities examined include: Depression, anxiety, obsessive compulsive disorder, schizophrenia, bipolar disorder, mood disorders,  psychoses,  diabetes, obesity, cardiovascular outcomes (coronary artery disease, peripheral vascular disease), hypertension, cancer, seizure disorders, insomnia, asthma, allergy, autoimmune diseases, gastrointestinal disorders (e.g. GERD), osteoporosis, chemical dependency, smoking, and  alcohol use. For comparisons of prevalence of co-morbidities and utilization of medical care services between adults with ASD and adults without ASD, we used all data recorded in the electronic medical record in the 24-month time period from January 2009-December 2011.  To assess provider knowledge about ASD, all adults primary and specialty care clinicians (~1700) were invited to complete a brief online survey (~10 questions, 2 minutes to complete).

Results:  The overall prevalence of ASD among adult members of KPNC as of March 2012 was 16/10,000. Prevalence varied by age category, with the highest prevalence in the 18-24 age group (81/10,000). Prevalence also varied by sex, with a male: female ratio of 3 to 1. Further data on the prevalence of medical comorbidities and healthcare utilization will be presented.  

Conclusions:  The prevalence of ASD in young adults is similar to that of school aged children. The final results from this study will contribute to filling important knowledge gaps in our understanding of the prevalence of psychiatric and medical co-morbidities and patterns of health care service utilization among this vulnerable population. Moreover, results from the provider survey will lead to the development of improved strategies for delivering the most appropriate and effective health care to this growing population.