Patterns and Characteristics of Adult Autism Spectrum Disorders (ASD) Related Hospitalizations: A 10 Year Nationwide Trend Analysis

Background: Despite rising prevalence of ASD, older age being associated with greater hospitalization risk, and greater number of children transitioning to adulthood; extremely few studies (restricted) have examined the utilization of hospital resources by adults with ASD. There is a critical need to examine the patterns in ASD related hospitalizations over time, especially as compared to other adult psychiatric disorders.   

Objectives: To examine trends in prevalence rates of ASD as compared to seven other psychiatric disorders for: number of hospitalizations, length of stay (LOS), total hospital charges, and mortality for adults aged 22-64 years over a 10 year period (year 2000-2009). To identify predictors of total hospital charges, length of stay, and mortality associated with ASD-related hospitalizations in a pooled sample (year 2000-2009). 

Methods:  A retrospective cross sectional analysis using nationally representative hospitalization data from the Health Care Utilization Project, Nationwide Inpatient Sample (HCUP-NIS), AHRQ was performed. The HCUP-NIS is the largest publicly available all-payer inpatient health care database in the US which contains de-identified data from more than 1,000 hospitals, representing a 20% stratified sample of discharges from community hospitals. Study sample included all hospitalizations associated with any diagnosis (ICD-9-CM codes) of eight adult psychiatric disorders: ASD, Schizophrenia, Intellectual Disability (ID), Anxiety Disorders, Bipolar Disorder, Depression, Substance Abuse Disorders, and Attention Deficit Hyperactivity Disorder/ Attention Deficit Disorder (ADHD/ADD). ASD-related hospitalizations were identified as any visit associated with an ICD-9-CM code for 299.xx. Other psychiatric disorders were identified with their respective ICD-9-CM codes, excluding any comorbid ASD diagnoses. Two sample chi-square tests,logistic and ordinary least square regressions were used for bivariate and multivariate analyses. All analyses were adjusted for complex survey design and weights. 

Results: Overall, the study sample consisted of 11,138 adult ASD-related hospitalizations. Rates of ASD-related hospitalizations increased significantly from 3,945 to 19,307 per 1,000 psychiatric admissions over the 10-year period as compared to all other psychiatric disorders except ADHD/ADD (3,040 to 20,858 per 1,000 psychiatric admissions). Although the average total inflation adjusted hospital charges for ASD-related hospitalizations increased significantly (p<0.01), the average length of stay, and mortality events were found to decline over the 10 year period (p<0.01). ASD-related hospitalizations in general recorded a greater length of stay (7.7 days vs 5.5 days, p<0.001), average total hospital charges ($29,541 vs. $24,030, p<0.001), and mortality events (1.4% vs. 0.7%, p<0.001) as compared to all other psychiatric disorders.  Significant predictors for hospital charges were younger age (β=-0.104, p <0.05) and presence of co-occuring conditions such as cancer (β=0.433, p <0.001) and gastrointestinal conditions (β=0.106, p <0.001). Significant predictors for ASD-related mortality included number of diagnostic procedures (AOR=1.29, 95% CI=1.21-1.39), admission via emergency room (AOR=1.71, 95% CI: 1.04-2.80), and presence of a co-occurring condition such as a respiratory disorder (AOR= 4.99; 95% CI=3.04-8.21) and a cardiovascular condition (AOR=2.63, 95% CI=1.68-4.12). 

Conclusions: The prevalence of ASD-related hospitalizations is rising among adults. Healthcare providers and policymakers should ensure provision of optimum outpatient services and better care coordination to reduce delayed/foregone care and preventable hospitalizations among adults with ASD.