The Impact of Intellectual Disability on the Health Service Utilization of Middle Aged and Older Adults on the Autism Spectrum

Background: Preliminary evidence suggests that autistic adults live shorter lives and have more physical and mental health problems compared to the general population. Since so little is known about the larger population of middle aged and older adults on the autism spectrum, it is imperative to leverage existing population-level data to characterize their health service utilization to inform individual and systems-level prevention efforts that can help people on the autism spectrum live long, healthy, and self-determined lives in their communities.

Objectives: This study describes the health service utilization of a unique sample of all middle aged and older Wisconsin Medicaid beneficiaries with an identified autism spectrum disorder diagnosis and tests differences between those autistic adults with and without co-occurring intellectual disability (ID).

Methods: Participants were 143 middle aged and older autistic adults aged 40-88 with two or more Medicaid claims for an ICD-9 code corresponding to an autism spectrum disorder on two different days with (N=64) and without ID (N=79). We examined service claims from all providers (inpatient, outpatient, long-term care, home health, and dental) for service use and physical and mental health conditions between 2012-2015. We categorized service use based on service type and tested differences between autistic adults with and without ID in frequency and type of service use. We categorized physical and mental health conditions based on an established system for grouping ICD-9 codes (Croen et al., 2015) while also presenting prevalent individual conditions.

Results: Autistic adults had, on average, 176.4 (SD=220.6) claims during the four-year study period. In the full sample of autistic adults with and without ID, 66.4% had dental, 43.9% had outpatient, 32.9% had inpatient, 13.3% had home health, and 7.7% had long-term care claims. Findings indicate that autistic adults with ID were more likely to have dental (X²=7.1, P=0.008) and home health (X²=7.4, P=0.007) claims compared to adults without ID. Many physical and mental health problems, including immune (70.6%), cardiovascular (49.0%), sleep (85.3%), gastrointestinal (49.7%), neurologic (55.9%), and psychiatric (72.0%) conditions were highly prevalent in our full sample. When comparing odds of the categorized conditions between those with and without ID, we saw increased but not statistically significant odds of neurologic and gastrointestinal conditions and decreased but not statistically significant odds for immune, cardiovascular, and psychiatric conditions in middle aged and older adults on the autism spectrum with co-occurring ID.

Conclusions: This is the first US study to use claims data to characterize the health and health service utilization of middle aged and older adults on the autism spectrum with and without intellectual disability. Our findings suggest that people on the autism spectrum have a high prevalence of health problems in midlife and old age, regardless of intellectual disability status. However, autistic adults with ID were more likely to have received dental and home health care. While more research is needed to confirm these findings and understand mechanisms, our results underscore the importance of prevention for high prevalence of physical and mental health problems in autism at the individual and systems level.