Health Care Service Utilization in an Integrated Healthcare Delivery System Among Adults with Autism Spectrum Disorders

Background: Adults with autism spectrum disorder (ASD) have a significantly higher burden of most major medical and psychiatric conditions compared to adults without ASD.  The reasons for this are not known, but may be related to less adequate utilization of preventive healthcare services or poorer control of chronic conditions.  Currently, very little is known about healthcare service utilization among this growing population. 

Objectives: To compare healthcare utilization patterns of adults with ASD and adults without ASD among a large and diverse population of adults receiving healthcare services in an integrated healthcare delivery system.

Methods: The study population was drawn from the adult membership (≥ 18 years) of Kaiser Permanente in Northern California (KP) who were enrolled in the health plan for at least 9 months each year from 2008-2012. ASD cases (N=1,507) were adults with at least two ASD diagnosis (ICD-9-CM 299.0-299.8) recorded in the electronic medical record by December 2012. A control group of adults without any ASD diagnoses (N= 15,070) was sampled at a 10:1 ratio and frequency matched to cases on total length of KP membership, sex, and age. Health care utilization data were obtained from the KP inpatient and outpatient databases for the year 2012. Utilization occurring at KP facilities and authorized non-KP facilities was defined in terms of the percentage of patients with outpatient clinic visits, hospitalizations, emergency department visits, and specialty care visits in the study year.  Proportions of each healthcare service utilization category were compared between cases and controls after adjusting for several covariates using multivariable logistic regression models.  Covariates included age, sex, race/ethnicity, total length of membership, and eight categories of medical and psychiatric comorbidities (immune conditions, cardiovascular diseases, metabolic disorders, neurologic diseases, gastrointestinal disorders, sleep disorders, nutritional conditions, and psychiatric conditions).

Results: Compared to controls, adults with ASD had significantly higher utilization of outpatient visits for primary care (74% vs.59.1%), mental health (43.3% vs. 5.4%) and neurology (5.6% vs. 1.5%).  Utilization of hospice/home healthcare (1.3% vs. 0.3%), skilled nursing services (0.6% vs. 0.1%) and speech therapy (0.8% vs. 0.1%) were uncommon but all significantly higher among adults with ASD compared to adults without ASD. The higher rate of utilization in these categories was evident among both men and women.  Among men only, utilization of inpatient hospitalizations (4.8% vs. 1.9%) and laboratory services (55.5% vs. 38.9%) was significantly higher among ASD cases than controls, and utilization of physical or occupational therapy services was significantly lower (2.8% vs. 4.2%).  Among women, utilization of gynecology services was significantly lower among ASD cases compared to controls (35.1% vs. 49.1%).  Finally, for most healthcare service utilization categories, case-control differences were most pronounced for adults over 50 years of age. 

Conclusions: With the exception of gynecologic service utilization among women, adults with ASD have higher utilization of most healthcare services compared to controls, even after controlling for medical and psychiatric comorbidities.  More research is needed to determine reasons for these utilization differences and to develop strategies to improve delivery of health care to adults with ASD.