Healthcare service use patterns among autistic adults: A systematic review with narrative synthesis

Abstract

Autistic adults often experience barriers to healthcare that can cause their healthcare service use to be unique from other populations. We conducted a systematic review to gather the most recent evidence about how often autistic adults use five important healthcare services (the emergency department, hospitalization, outpatient mental health, preventive services, and primary care) compared to populations of non-autistic adults. We searched six electronic research databases for articles. Our search strategy identified N = 2964 unique articles. Ultimately, we included N = 16 articles in our review. Most included studies (N = 13) were high-quality level 3a studies that compared autistic adults’ service use to a non-autistic population comparison group (N = 11), and examined emergency department use (N = 12). Autistic adults most often had equal or higher use of services than population comparison groups across all healthcare services we examined. Although autistic adults had greater use of primary care and preventive services than comparison groups, frequent emergency department visits and hospitalizations may reflect that these services are not adequately meeting autistic adults’ needs. Future research should identify targets for improving autistic adults’ access to and use of primary care and preventive services, which may ultimately reduce frequent use of the emergency department and hospitalizations.

Lay abstract

Autistic adults often have complex healthcare needs due to factors like having other health conditions, sensory sensitivities, and limited access to healthcare providers who are trained to provide care for them. All these factors may influence the healthcare services that autistic adults use. In this review, we searched six electronic research databases to gather the most recent evidence about how often autistic adults use five important healthcare services (the emergency department, hospitalization, outpatient mental health, preventive services, and primary care) compared to populations of non-autistic adults. A total of 16 articles were ultimately included in this review. Most articles found that autistic adults had equal or higher use of healthcare services than non-autistic adults. Autistic adults frequently used the emergency department and hospital. This may indicate that routine outpatient care in the community is not meeting their needs. Our findings show the importance of improving care at this level for autistic adults to reduce overuse of the emergency department (in this article referred to as ED) and hospital.

Keywords

autism health services systematic review

Introduction

Each year approximately 50,000 autistic individuals in the United States reach adulthood (Interagency Autism Coordinating Committee [IACC], 2017). Reaching adulthood has implications for many aspects of autistic adults’ lives, including their interaction with the healthcare system. Autistic adults often have a high number of co-occurring physical and mental health conditions (Bishop-Fitzpatrick & Rubenstein, 2019; Croen et al., 2015; Hand, Angell, Harris, & Carpenter, 2020; Lai et al., 2019) that require access to healthcare services that are tailored to meet their unique needs as autistic individuals. For example, autistic adults might require individualized methods of communication with their healthcare providers (Nicolaidis et al., 2015), more time to process information (Dern & Sappok, 2016), or modifications to portions of healthcare visits to accommodate sensory sensitivities (Saqr, Braun, Porter, Barnette, & Hanks, 2018). Patient-centered accommodations like these are necessary for the healthcare system to provide high-quality patient-centered care for this growing population.

However, the healthcare system in the United States is largely unprepared to meet autistic adults’ unique healthcare needs, an issue that has been voiced nationally as important to address (IACC, 2017). Few adult healthcare providers are trained to provide care for autistic adults (Unigwe et al., 2017; Zerbo, Massolo, Qian, & Croen, 2015). As a result, autistic adults often experience disparities in access to services when they reach adulthood (Nathenson & Zablotsky, 2017). These disparities contribute to autistic adults’ high rates of unmet healthcare needs (Nicolaidis et al., 2013) and frequent use of services like the emergency department (Liu, Pearl, Kong, Leslie, & Murray et al., 2017). Such service use patterns may result in autistic adults incurring high healthcare costs for suboptimal healthcare (Zerbo et al., 2018).

A better understanding of autistic adults’ healthcare service use patterns is necessary to prepare the healthcare system and its providers to meet this population’s needs. This systematic review is, therefore, a valuable contribution to the literature, as it systematically identifies and synthesizes the available evidence pertaining to autistic adults’ healthcare service use patterns. Findings from this review will offer a clear picture to researchers, clinicians, and other stakeholders of how this growing population interacts with the healthcare system compared to other populations. This information is valuable because it will inform needed changes to the healthcare system both now and in the future; providing direction for targeted efforts to increase autistic adults’ access to patient centered care and emphasizing the need for providers to be trained to care for this population. These factors provide the rationale for this review, and led the researchers to pose the review question, “How do healthcare service use patterns among autistic adults differ from other populations?”

Methods

We conducted a systematic review of the literature on the healthcare service use patterns of autistic adults compared to non-autistic adult populations. Our review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (Moher, Liberati, Tetzlaff, Altman, & PRISMA Group, 2009). The study protocol for this review is registered with PROSPERO, the International Prospective Register of Systematic Reviews (registration # CRD42020213499).

Inclusion criteria

Studies were included in this review if they met the following inclusion criteria: (1) included a discrete sample of autistic adults or a sample consisting primarily of autistic adults (i.e. > 50%; adulthood was defined conventionally as ⩾ 18 years of age), (2) had a quantitative design, (3) reported frequency of use of the specified health service area(s) among autistic adults, (4) compared use of the service area(s) to a non-autistic adult comparison group, and (5) described service use patterns in the United States. Services of interest included (1) ED use, (2) hospitalizations, (3) primary care, (4) preventive services, and (5) outpatient visits for mental health conditions. While other services could have been included in this review, these services were chosen intentionally, as they are services that have been described in the available literature as identified by the authors’ preliminary literature review.

Exclusion criteria

Studies were excluded if they did not include any autistic adults, or if the sample was comprised primarily of non-autistic adults (e.g. the sample was comprised of adults who have different kinds of developmental disabilities of which autism was not the majority). Qualitative studies, unpublished research, non-peer reviewed research, reviews, non-human studies, books, case studies, and presentations were excluded. Studies that did not utilize US healthcare data and those that did not compare autistic adults’ healthcare service use to a non-autistic adult comparison group were also excluded.

Search strategy

In accordance with best practice (Moher et al., 2009), we developed our search strategy with the assistance of a research librarian. We searched for articles in six distinct research databases to promote a comprehensive search of the available literature. These databases included PubMed, Embase, Web of Science, Scopus, CINAHL, and Psyc Info. The search strategy was modified slightly for two databases (PubMed and Embase) due to their unique indexing terms and search refinement capabilities. All searches were conducted by D.G. on 15 October 2020 and contained phrases and keywords pertaining to autism, adulthood, and the specified healthcare services. We also reviewed the reference lists of included articles to identify any additional studies that fit the inclusion criteria but were not captured in the electronic database searches. To gather the most recent evidence pertaining to autistic adults’ healthcare service use patterns, we refined the database searches to only include articles that were published from the years 2010 and 2020. An example search strategy (PubMed) is provided below. The search strategies for all databases and number of articles identified from each before deduplication is available in the Supplementary Materials.

Example Search Strategy (Pubmed)

(autism spectrum disorder[mesh] OR autism[tw] OR autistic[tw] OR asd[tw]) AND (adult[mesh] OR adult[tw] OR adults[tw] OR adulthood[tw]) AND (hospitalization[mesh] OR emergency service, hospital[mesh] OR emergency medical services[mesh] OR emergency medicine[mesh] OR emergency treatment[mesh] OR emergency[tw] OR emergencies[tw] OR primary healthcare[mesh] OR primary care[tw] OR primary healthcare[tw] OR primary health care[tw] OR preventive health services[mesh] OR preventive[tw] OR preventative[tw] OR mental health services[mesh] OR mental health services[tw] OR mental healthcare[tw] OR mental health care[tw] OR mental health[mesh] OR patient acceptance of healthcare[mesh] OR utilization[tw] OR utilisation[tw] OR health services for persons with disabilities[mesh]) NOT “adult spinal deformity”

Study screening

One rater (D.G.) imported batches of retrieved articles into the Covidence systematic review platform so that retrieved articles could be screened in an organized and efficient manner. The Covidence platform has an algorithm that automatically removes duplicate articles and imports them into the first stage of study screening, which for this review was title and abstract screening. D.G. and one other rater (M.K.) independently reviewed article titles and abstracts to determine inclusion vs exclusion using a checklist developed specifically for this study (Table 1). Items within the checklist were divided into an inclusion and an exclusion section. Items could be marked as “Yes,” “No,” or “Cannot Tell.” If any items were marked as “Yes” in the exclusion section of the table, the rater marked the article for exclusion within Covidence. If none of the items in the exclusion section were marked as “Yes,” and all those in the inclusion section were marked as “Yes,” the rater included the article within Covidence. Articles for which items were marked as “Yes” or “Cannot Tell” in the inclusion section, or for which items in the exclusion section were marked “Cannot Tell” but none were marked “Yes” received a vote of “Maybe.” Articles that were marked for inclusion by both raters, marked as “Maybe” by both raters, or marked for inclusion by one rater and “Maybe” by the other rater proceeded to the full text review stage.

Table 1.

Questions used for title and abstract screening.

Inclusion:	Yes	No	Cannot tell
Does the study describe a discrete sample of autistic adults of which the majority are ⩾ 18 years old?
Does the study compare autistic adults’ healthcare utilization to that of a comparison group?Was the study conducted in the United States using US healthcare data?
Exclusion	Yes	No	Cannot tell
Does the study describe a sample that is not comprised of autistic adults or of which less than half are autistic adults?
Does the study report healthcare utilization outcome(s) among autistic adults without reference to a comparison group?Is the source a qualitative study, unpublished research, a review, non-human study, book, case study, or presentation?Was the study conducted outside of the United States using healthcare data from another country?Full text article available in English?

Conflicts were defined as one rater marking an article for inclusion or “Maybe” and the other marking the article for exclusion within Covidence. If D.G. and M.K. disagreed on whether an article should proceed to the full text review stage, they attempted to resolve the conflict via discussion. If consensus was not achieved via discussion, another rater (B.N.H.) provided a third vote to determine whether the article would be excluded or moved on to the full text review stage. This process is depicted in Figure 1.

Figure 1.

Title and abstract screening process.

Full text review

At the full text review stage, a similar screening process was utilized. D.G. and M.K. independently reviewed the full text articles to determine if they would be excluded or move forward to the data extraction phase. A checklist like the one used in the title and abstract screening phase was developed for use at the full text review stage (Table 2). To proceed to data extraction, all items in the inclusion section of the checklist had to be marked as “Yes,” and none of the items in the exclusion section could be marked as “Yes.” This process is depicted in Figure 2. Conflicts were defined as one rater marking “Yes” and the other marking “No.” Conflicts were resolved in the same manner as they were in the title and abstract screening phase, with B.N.H. providing a third vote when D.G. and M.K. did not reach consensus via discussion.

Figure 2.

Full text review process.

Table 2.

Questions used for full text screening.

Inclusion:	Yes	No
Does the study describe a discrete sample of autistic adults of which the majority are ⩾ 18 years old?
Does the study employ quantitative research methods?
Does the study report autistic adults’ frequency of utilization of one of the specified outcome areas?
Does the study compare autistic adults’ healthcare utilization to that of a comparison group?Was the study conducted in the United States using US healthcare data?
Exclusion	Yes	No
Does the study describe a sample that is not comprised of autistic adults or of which less than half are autistic adults?
Does the study report healthcare utilization outcome(s) of interest among autistic adults without reference to a comparison group?Is the source a qualitative study, unpublished research, a review, non-human study, book, case study, or presentation?Was the study conducted outside of the United States using healthcare data from another country?Full text article available in English?

Evidence appraisal

Included studies were assessed for quality by the lead author using the LEGEND (Let Evidence Guide Every New Decision) evidence appraisal tools from Cincinnati Children’s Hospital (Clark, Burkett, & Stanko-Lopp, 2009). The LEGEND quality assessment tools are specific to study design and support a thorough assessment of the quality of research studies, evaluating critical features salient to study quality such as congruency of the research question(s) with the study design, sample selection procedures, and appropriateness of statistical methods. Results from the evidence appraisals for included studies were used to inform the interpretation of the results of each study. According to the LEGEND system, levels of research evidence can range from 1a (e.g. high quality systematic reviews) to 5b (e.g. case reports). Smaller numbers indicate more rigorous study designs. Articles are also denoted with either an “a” (indicating “good quality), or a “b” (indicating “lesser quality”).

Data extraction and synthesis

One rater (D.G.) used the Covidence data extraction platform to extract the following data from studies that proceeded to the data extraction phase: (1) study purpose, (2) data source, (3) study sample, (4) sample demographic characteristics, (5) service(s) examined, and (6) key findings. These data were exported from Covidence into an Excel spreadsheet and then organized into an evidence table.

We took a narrative approach to synthesize and analyze the results of this review. Our approach was informed by the European Social Research Council’s guidance on conducting narrative syntheses in systematic reviews (Popay et al., 2006). First, we conducted a preliminary synthesis, whereby included studies were tabulated and organized by service type (Table 3). Second, we looked for broad patterns in the data across service categories (e.g. study size and data source). Finally, we investigated relationships in the data among individual service categories and used these data along with the quantity (i.e. number of studies) and quality (i.e. results of critical appraisals) of the evidence to guide our conclusions.

Table 3.

Evidence table.

Emergency department use
Reference (Author, year)	Study purpose	Data source	Sample characteristics	Key findings	Quality score
Benevides, Carretta, Graves, & Sikka (2020)	To identify rates of ED utilization among transition-age adults with ASD, ASD + ID, and ID only	Medicare data (2010)	N = 3499 ASD individuals (78% male; mean age = 23)N = 2048 ASD individuals with co-occurring ID (74% male; mean age = 23)N= 13,178 individuals with ID (55% male; mean age = 24)	Adults with ASD or ASD + ID had fewer annual ED visits than adults with ID-only (p < 0.001)	3b
Nakao et al. (2014)	To compare the rates and associated costs of NTDC-related ED visits among individuals with and without ASD	NEDS (2010)	N = ASD individuals reported as < 0.1% of adult sample of 103,450,324(% male not reported; mean age not reported)N = non-ASD individuals reported as < 0.4% of adult sample of 103,450,324(% male not reported;mean age: not reported)	ASD adults had reduced odds of a NTDC-related ED visit compared to the PC (p < 0.001).	3a
Liu et al. (2017)	To examine rates of ED utilization in ASD individuals compared to individuals without ASD	MarketScan claims data (2005–2013)	N = 87,683 ASD individuals(80% male; mean age = 14)N= 56,178,622 non-ASD individuals (51% male; mean age = 16)	ASD adults 18–21 years old used the ED at increasing rates over the study period (as high as > 30% in a given year) where adults of the same age in PC group had static utilization over the study period (3–4% per year) (p < 0.0001)	3a
Deavenport-Saman, Lu, Smith, & Yin (2016)	To examine factors associated with ED utilization among individuals with and without ASD	2006–2009 administrative ED discharge data	N= 2426 ASD individuals (84% male; mean age not reported)N = 155,476 non-ASD individuals (54% male; mean age not reported)	ASD adults did not statistically differ from PC adults on rates of ED visits per year	3a
Iannuzzi, Cheng, Broder-Fingert, & Bauman (2015)	To identify the most commonproblems for which ASD and non-ASD individuals present in the ED	NEDS (2010)	N = 109,021 ASD individuals (79% male; mean age not reported)N = 128,849,332 non-ASD individuals (45% male; mean age not reported)	A smaller proportion of all ED visits among ASD group were for adults (31%) compared to all ED visits among PC group (89%)^a	3a
Mental health visits
Reference (Author, year)	Study purpose	Data source	Sample characteristics	Key findings	Quality score
Maddox, Kang-Yi, Brodkin, & Mandell (2018)	To identify differences in psychiatric treatment use between adults with anxiety and depression with and without ASD	Medicaid data (2008–2009)	N = 268 ASD individuals (69% male; mean age not reported)N= 1072 non-ASD individuals (69% male; mean age not reported)	ASD adults were less likely to receive talk therapy for anxiety/depression or group therapy (p < 0.05), but more likely to receive case management (p < 0.001) for mental health conditions than the PC; Among those receiving talk therapy, ASD adults averaged more visits per month (p < 0.001)	3a
Shea et al. (2018)	To compare healthcare service utilization and costs between individuals with either ASD or ID	Medicaid data (2001 and 2005)	N = 2054 ASD individuals (78% male; mean age not reported)N = 12,316 individuals with ID (56% male; mean age not reported)	80% of ASD adults utilized psychiatric outpatient services compared to 69% of adults in the ID group; Outpatient psychiatric utilization decreased by 19% among the ASD group over 4 years, but by 27% among the ID group^a	3a
Esbensen, Bishop, Seltzer, Greenberg, & Taylor (2010)	To examine differences between adults with Down syndrome and ASD adults on functional abilities and health service usage	ASD data from 2000 to 2001 (Seltzer et al., 2003; parent interviews)Down syndrome (DS) data from 1997 to 1998 (Krauss & Seltzer, 1999)	N = 70 ASD individuals (69% male; mean age = 37)N = 70 individuals with DS (66% male; mean age = 37)	ASD adults were more likely to receive psychological or psychiatric services than adults with DS (p < 0.001)	3b
Hospitalizations
Reference (Author, year)	Study purpose	Data source	Sample characteristics	Key findings	Quality score
Shields, Akobirshoev, Dembo, & Mitra (2019)	To compare hospital admissions related to self-injurious behavior and ideation among adults with and without ASD	NIS (2014)	N = 5341 ASD individuals (74% male; mean age not reported)N = 16,023 non-ASD individuals (74% male; mean age not reported)	ASD adults were nearly twice as likely as PC adults to be hospitalized for self-injurious behavior and ideation (p ⩽ 0.001)	3a
Multiple outcomes
Reference (Author, year)	Study purpose	Data source	Sample characteristics	Key findings	Quality score
Hand, Boan, Bradley, Charles, & Carpenter (2019)	To compare the incidence of ACS-admissions among four cohorts: ASD-only, ASD + ID, ID-only, and PCs	State-level administrative billing data (2000–2015)	N = 241 ASD individuals (85% male; mean age not reported)N = 243 ASD individuals with co-occurring ID (78% male; mean age not reported)N = 1148 individuals with ID (63% male; mean age not reported)N = 2255 PCs (81% male; mean age not reported)	ED utilization:ASD and PC adults did not statistically differ on risk of having an ACS-ED visit; proportion of individuals who had an ACS-ED visit:14.9% (ASD), 9% (ASD + ID), 23.2% (PC), 14% (ID)^a Hospitalization:ASD adults with co-occurring ID were more likely to have an ACS-hospitalization than PC adults (p < 0.01), but ASD adults without co-occurring ID did not differ from PC on risk of an ACS-hospitalization; proportion of individuals who had an ACS-hospitalization:2.6% (ASD), 10% (ASD + ID), 7% (PC), 5.8% (ID)^a	3a
Multiple outcomes
Reference (Author, year)	Study purpose	Data source	Sample characteristics	Key findings	Quality score
Vohra, Madhavan, & Sambamoorthi (2016)	To examine trends, type of ED visits, and average ED charges for adults with and without ASD	NEDS (2006–2011)	N = 25,527 ASD individuals (76% male; mean age not reported)N = 76,581 non-ASD individuals (76% male; mean age not reported)	ED utilization:ASD adults’ and PC adults’ rates of ED visits increased over time at similar ratesHospitalization:34% of ASD ED visits led to a hospitalization where only 11% of ED visits among PC adults led to a hospitalization^a	3a
Vohra, Madhavan, & Sambamoorthi (2017)	To examine the prevalence and association of co-occurring conditions with healthcare utilization patterns and expenditures of ASD adults and non-ASD adults	Medicaid data (2000–2008)	N = 1772 ASD individuals (71% male; mean age not reported)N = 5320 non-ASD individuals (71% male; mean age not reported)	ED utilization:ASD adults and PC adults did not statistically differ in terms of mean number of ED visits per yearHospitalization:ASD adults significantly less likely to be hospitalized than PC adults (p < 0.001)	3a
McDermott et al. (2015)	To compare hospital encounters (hospitalizations and ED visits) among adolescents and young adults with ASD and either FXS, ID, or PC	State-level data (Medicaid and State health plan 2000–2010)	N = 2592 ASD individuals (76% male; mean age not reported)N = 125 individuals with FXS (71% male; mean age not reported)N= 10,685 individuals with ID (58% male; mean age not reported)N= 26,804 PC individuals (62% male; mean age not reported)	ED utilization:Relative to PC adults, ASD adults were more likely to have an ED visit OR = 1.5 (95% CI = 1.3–1.7); adjusted rates of ED visits compared to other groups: (18.4%_ASD vs 27.9%_ID), (19.4%_ASD vs 17.0%_FXS)^a Hospitalization:Relative to the PC, ASD adults had higher odds for an inpatient hospitalization OR = 5.7 (95% CI = 4.5–7.3); adjusted rates of hospitalization compared to other groups: (6.7%_ASD vs 12.7%_ID), (6.7%_ASD vs 7.3%_FXS)^a	3a
Ames, Massolo, Davignon, Qian, & Croen (2021)	To examine differences in healthcare utilization among four cohorts: ASD, ADHD, DM, and PCs	KPNC Health System (2014–2015)	N = 4123 ASD individuals (81% male; mean age = 18)N = 20,615 individuals with ADHD (81% male; mean age = 18)N = 2156 individuals with DM (48% male; mean age not reported)N= 20,516 PC individuals (81% male; mean age = 18)	ED utilization:ASD adults less likely to use ED than ADHD OR = 0.66 (95% CI = 0.60–0.73) and DM OR = 0.50 (95% CI = 0.43–0.58) adults, but did not statistically differ from PCHospitalizations:ASD adults more likely to be hospitalized than ADHD OR = 1.81 (95% CI = 1.52–2.16) and GP OR = 2.45 (95% CI = 2.01–2.97), but less likely to be hospitalized than DM adults OR = 0.66 (95% CI = 0.52–0.83)Mental health visits:ASD adults had higher odds of utilization and mean number of mental health visits than all comparison cohorts: PC: OR = 10.87 (95% CI = 9.90–11.94), AMR: 7.1 (p < 0.0001); ADHD: OR = 1.73 (95% CI = 1.60–1.86), AMR = 1.63 (p < < 0.0001); DM: OR = 4.65 (95% CI = 3.96–5.45), AMR = 2.53 (p < 0.0001)Primary care:ASD adults had greater primary care utilization than PC adults OR = 1.38 (95% CI = 1.27–1.49) and ADHD adults OR = 1.09 (95% CI = 1.01–1.18), but lower than that of DM adults OR = 0.42 (95% CI = 0.36–0.48)Preventive services:ASD adults more likely to receive well-adult medical exam OR = 2.07 (95% CI = 1.86–2.30), flu vaccine OR = 1.82 (95% CI = 1.69–1.96), less likely to have pelvic exam OR = 0.53 (95% CI = 0.40–0.70) than GP adults; More likely to receive well-adult medical exam OR = 2.11 (95% CI = 1.90–2.34), flu vaccine OR = 1.54 (95% CI = 1.43–1.66), less likely to receive pelvic exam OR = 0.52 (95% CI = 0.40–0.69) than ADHD group More likely to receive flu vaccine OR = 1.15 (95% CI = 1.02–1.29), but less likely to receive pelvic exam OR = 0.71 (95% CI = 0.52–0.97) than DM adults	3a
Zerbo et al. (2018)	To compare health care utilization patterns and cost among insured adults with ASD, adults with ADHD, and PC adults with neither condition	KPNC Health System (2012)	N = 1507 ASD individuals (73% male; mean age = 29)N = 9042 individuals with ADHD (73% male; mean age = 29)N = 15,070 PCs (73% male; mean age = 29)	ED utilization:ASD adults did not statistically differ from ADHD or PC adults on odds of ED useHospitalization:ASD adults more than twice as likely as ADHD adults OR = 2.1 (95% CI = 1.6–2.9) to be hospitalized for an ACS diagnoses, but no differences were found when compared to PC adultsMental health visits:ASD adults had higher utilization and mean number of visits for mental health than ADHD adults: OR = 1.6 (95% CI = 1.4–1.8), AMR = 1.9 (95% CI = 1.7–2.2) and PC adults: OR = 11.5 (95% CI = 10.0–13.2), AMR = 11.7 (95% CI = 9.3–14.8)Primary care:ASD adults had higher utilization of primary care than ADHD OR = 1.2 (95% CI = 1.1–1.3) and PC OR = 1.3 (95% CI = 1.2–1.4) adultsPreventive services:ASD adults more likely to receive an influenza vaccination OR = 2.6 (95% CI = 2.3–2.9), cholesterol screening OR = 1.7 (95% CI = 1.2–2.5), and diabetes screening OR = 1.8 (95% CI = 1.3–2.5) than PC adults, but less likely to have cervical cancer screening OR = 0.6 (95% CI = 0.5–0.8); more likely to receive flu vaccine OR = 2.3 (95% CI = 2.1–2.7), cholesterol screening OR = 1.7 (95% CI = 1.2–2.5), diabetes screening OR = 1.8 (95% CI = 1.3–2.5) but less likely to receive cervical cancer screening OR = 0.7 (95% CI = 0.5–0.9) than ADHD adults	3a
Nicolaidis, et al. (2013)	To assess the healthcare experiences (e.g. patient–provider communication, healthcare utilization patterns) of autistic adults versus those of non-autistic adults	Online survey	N = 209 ASD individuals (41% male; mean age = 37)N = 228 non-ASD individuals (34% male; mean age = 40)	ED utilization:ASD adults had a greater odds of using the ED than PC adults OR = 2.1 (95% CI = 1.8–3.8)Hospitalization:ASD and PC adults were equally likely to have been hospitalized in the past yearPreventive services:ASD adults were less likely to receive a tetanus vaccination OR = 0.05 (95% CI = 0.3–0.9) or a pap smear OR = 0.5 (95% CI = 0.2–0.9) than PC adults	3b

ED: emergency department; ASD: autism spectrum disorder; ID: intellectual disability; NTDC: non-traumatic dental condition; NEDS: National Emergency Department Sample; PC: population comparison group; NIS: National Inpatient Sample; FXS: Fragile X syndrome; OR: odds ratio; CI: confidence interval; ADHD: attention deficit hyperactivity disorder; KPNC: Kaiser Permanente Northern California; ACS: ambulatory care sensitive; DM: diabetes mellitus; AMR: adjusted mean ratio; 3a: higher quality cross-sectional study; 3b: lower quality cross-sectional study.

Reported findings are descriptive statistics only.

Results

The results of our search strategy at each stage of the review are shown in Figure 3. Our search strategy identified 2964 unique articles, and we ultimately included 16 articles in this systematic review.

Figure 3.

PRISMA diagram.

Description of included studies

Important features of included studies can be found in Table 3. All studies employed cross-sectional designs. Data sources were predominantly at the state or national level (e.g. Medicaid claims), with two studies collecting data via interview or survey. ED use was examined in 12 studies, hospitalization in 8 studies, mental health visits in 5 studies, preventive services in 3 studies, and primary care visits in 2 studies. Across all studies, more than 248,000 autistic adults were included (one study did not report a specific sample size). Eleven studies compared health service use between only an autism and non-autism population comparison group (PC), and three studies (Ames et al., 2021; Benevides et al., 2020; Zerbo et al., 2018) included an autism group with more than one comparison group (e.g. attention-deficit/hyperactivity disorder (ADHD) and PC). Two studies reported only descriptive statistics as indicators of service use between autistic and non-autistic groups (Iannuzzi, et al., 2015; Shea et al., 2018). Studies varied markedly in their report of participant demographic characteristics, with 10 studies not reporting the mean age of autistic or non-autistic adults. Among the studies that reported the mean age of autistic adults, mean age ranged from 14 to 37. Proportions of males in the samples of autistic adults were between 41% and 85%, and proportions of autistic individuals who identified as White were between 37% and 94%. Among studies that reported geographic location, autistic adults most often lived in an urban versus a rural residence.

Quality of the evidence

Studies were assessed for quality using the LEGEND (Clark et al., 2009) critical appraisal tools. Critical appraisals revealed that this review included 13 “good-quality” cross-sectional studies (3a), and three “lesser-quality” cross-sectional studies (3b) as shown in Table 3.

Large sample sizes of autistic adults were a strength across studies, with 12 out of 16 studies including over 1000 autistic adults. The smallest sample of autistic adults was N = 70 (Esbensen et al., 2010). Case ascertainment procedures were a strength across the majority of included studies as well, primarily done via one or two (Liu et al., 2017; Shea et al., 2018; Zerbo et al., 2018) occurrences of an ICD-9 CM code (299.xx). One study required a clinical interview with diagnosis by a healthcare or education professional (Esbensen et al., 2010), and one reviewed clinical evaluation records against Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV) criteria (Hand et al., 2019). One study used participant self-report for case ascertainment (Nicolaidis et al., 2013). A majority of studies matched autistic adults to comparison groups on relevant demographic characteristics at ratios ranging from 1:1 to 10:1.

Three studies were rated “lesser quality” primarily because of convenience sampling via the Internet (Nicolaidis et al., 2013), vagueness regarding recruitment procedures and a relatively small sample size (Esbensen et al., 2010), and limited generalizability coupled with usage of old datasets (Benevides et al., 2020). Two of these studies (Esbensen et al., 2010; Nicolaidis et al., 2013) relied on participant self-report, which may have resulted in inaccurate report of healthcare service use patterns.

Study findings

Findings are organized below by healthcare service type. Three comparison groups (diabetes mellitus (DM), Down Syndrome (DS), and Fragile X syndrome (FXS)) were included in only one study each. Service use patterns among autistic adults relative to these populations as well as significance values for all studies are available in Table 3. Table 4 displays trends in autistic adults’ odds or frequency of service use relative to PC or ADHD comparison groups.

Table 4.

Autistic adult service use trends relative to PC or ADHD comparison groups (statistically significant odds or frequencies).

ASD vs PC
	Lower	Equal	Higher
ED	∙	∙∙∙∙∙∙	∙∙◦
Hospitalization	∙	∙∙◦	∙∙∙∙
Mental health			∙∙∙
Preventive services	◦		∙∙
Primary care			∙∙
ASD vs ADHD
	Lower	Equal	Higher
ED	∙	∙
Hospitalization		∙∙	∙∙
Mental health			∙∙
Preventive services			∙∙
Primary care			∙∙

PC: population comparison group; ADHD: attention-deficit/hyperactivity disorder; ASD: autism spectrum disorder; ED: emergency department.

∙ indicates 1 good-quality study and ○ indicates 1 lesser-quality study that found a statistically significant odds or frequency between ASD group vs comparison group.

ED use

Studies that compared ED use among autistic adults to that of comparison groups consisted of 10 level 3a studies and 2 level 3b studies (Table 3). Among these studies, findings were inconsistent. Only one study (level 3b; Benevides et al., 2020) examined autistic adults’ ED use relative to adults with ID-only and found that autistic adults used the ED at significantly lower rates. Two level 3a studies found that relative to adults with ADHD, autistic adults used the ED at lower (Ames et al., 2021) or equal rates (Zerbo et al., 2018). A larger number of studies examined autistic adults’ ED use relative to PC groups. Two level 3a studies found autistic adults to use the ED less often than PC groups (Iannuzzi et al., 2015; Nakao et al., 2014), but one of these (Iannuzzi et al., 2015) did not test for statistical significance. Three other studies (two 3a and one 3b) found a higher use of the ED among autistic adults (Liu et al., 2017; McDermott et al., 2015; Nicolaidis et al., 2013). However, most studies in this service category (six 3a), found no statistically significant difference in ED use between autistic adults and PC groups (Ames et al., 2021; Deavenport-Saman et al., 2016; Hand et al., 2019; Vohra et al., 2016, 2017; Zerbo et al., 2018).

Hospitalization

Seven level 3a studies and one level 3b study examined autistic adults’ hospitalization relative to comparison groups (Table 3). Most studies found that autistic adults had a greater odds of hospitalization (Ames et al., 2021; McDermott et al., 2015; Shields et al., 2019) or were hospitalized equally as often as PC groups (Nicolaidis et al., 2013; Zerbo et al., 2018). Hand and colleagues found that autistic adults with co-occurring ID (but not ASD alone) had greater odds of hospitalization relative to a PC group. Another level 3a study aligned with these trends, reporting higher rates of hospitalization after an ED visit among autistic adults, but did not perform significance testing (Vohra et al., 2016). One level 3a study found that autistic adults were hospitalized less frequently than PC comparison groups (Vohra et al., 2017). Relative to ADHD comparison groups, autistic adults had a higher likelihood of hospitalization for any reason (Ames et al., 2021) or for ambulatory-care-sensitive (ACS) diagnoses (Zerbo et al., 2018).

Outpatient mental health visits

All studies that compared autistic adults’ use of mental health services to that of PC, ADHD, or ID comparison groups were determined to be level 3a studies, and consistently found that autistic adults had greater use of these services. This included a significantly higher odds of use of outpatient mental health services (Ames et al., 2021; Zerbo et al., 2018), higher mean number of visits (Zerbo et al., 2018), and greater likelihood of case management for mental health conditions (Maddox et al., 2018) relative to the PC. In addition, autistic adults had a higher odds of use of mental health services than ADHD comparison groups (Ames et al., 2021; Zerbo et al., 2018). Autistic adults also used outpatient mental health services more often than adults with ID, but significance testing for these differences was not performed (Shea et al., 2018).

Preventive services

Studies comparing autistic adults’ use of preventive services to a comparison group consisted of two level 3a studies and one level 3b study. Studies examining vaccination use had inconsistent findings based on vaccination type. One level 3b study (Nicolaidis et al., 2013) found significantly lower rates of tetanus vaccination among autistic adults relative to a PC group. In contrast, two 3a studies found that autistic adults were significantly more likely to receive influenza vaccinations than PC and ADHD comparison groups (Ames et al., 2021; Zerbo et al., 2018). For other kinds of preventive services (i.e. pelvic exams, cervical cancer screenings, and pap smears), findings were more consistent. Autistic adults were significantly less likely to receive pelvic exams and cervical cancer screenings compared to PC and ADHD comparison groups (Ames et al., 2021; Zerbo et al., 2018), and were significantly less likely to receive pap smears relative to a PC group (Nicolaidis et al., 2013).

Primary care visits

Among two level 3a studies, autistic adults had a significantly higher odds of use of primary care services when compared to either PC or ADHD comparison groups (Ames et al., 2021; Zerbo et al., 2018).

Discussion

The 16 articles that were included in our systematic review suggest that relative to PC and ADHD comparison groups, autistic adults typically have a higher use of mental health, preventive, and primary care services. Autistic adults may have an equal or higher use of hospitalizations relative to these groups as well. Autistic adults may use the ED equally or less often than adults with ADHD, but equally or more often than PC groups. Use of some services (e.g. preventive services and primary care) was examined in a relatively small number of studies compared to other services (e.g. the ED). As such, patterns of autistic adults’ use of some services were less thoroughly characterized than others. However, our systematic review offers an important contribution to the literature, as it is informed by predominantly good-quality studies (13 out of 16). For the first time, this review offers a picture of what is currently known about autistic adults’ use of several important services in the US healthcare system. In addition, this review highlights facets of service use that should be researched in the future. We discuss below key factors that might contribute to the service use patterns observed in this review, as well as the implications of these patterns for autistic adults and the US healthcare system.

Service use—access does not mean quality

Our findings that autistic adults generally used healthcare services to an equal or greater degree than PC groups falls into alignment with what is currently known about this population’s health status. Specifically, that autistic adults experience a high number of physical and mental health conditions that co-occur with autism (Croen et al., 2015; Hand et al., 2020). As such, frequent use of services may indicate that this population is seeking the healthcare services that they need to manage or treat these conditions. Importantly, however, some of the services that autistic adults used more frequently than comparison groups were tertiary healthcare services (e.g. the ED and hospitals; Liu et al., 2017; Shields et al., 2019). Such services can be costly for autistic individuals who are frequently underinsured (Vohra et al., 2014), as well as for the healthcare system (Agency for Healthcare Research and Quality, 2020). Moreover, frequent use of such services may reflect a crucial issue: although autistic adults frequently use lower-level healthcare services (e.g. primary care and outpatient mental healthcare) (Vogan, Lake, Tint, Weiss, & Lunsky, 2017), the care that they receive in these contexts may be inadequate to meet their needs and to prevent frequent use of tertiary healthcare services. Indeed, autistic adults have frequently reported unmet healthcare needs (Jose et al., 2021; Schott, Nonnemacher, & Shea, 2021) in myriad settings such as primary care (Duker, Kim, Pomponio, Mosqueda, & Pfeiffer, 2019; Nicolaidis et al., 2015) and secondary care (i.e. specialist services; Camm-Crosbie, Bradley, Shaw, Baron-Cohen, & Cassidy, 2019).

Primary care and autistic adults’ use of tertiary health services

Among other populations, increased primary care use has been associated with less frequent use of tertiary healthcare services (Fishman, McLafferty, & Galanter, 2018; Galarraga, Mutter, & Pines, 2015; van den Berg, van Loenen, & Westert, 2016), but we did not observe this pattern. While level 3a studies consistently indicated that autistic adults had a greater use of primary care than population comparison groups (Ames et al., 2021; Zerbo et al., 2018), they typically had equal or more frequent use of the ED and hospital relative to these groups as well (Ames et al., 2021; Deavenport-Saman et al., 2016; McDermott et al., 2015; Shields et al., 2019; Vohra et al., 2016). In the case of hospitalizations, some studies found that autistic adults were more likely than comparison groups to be hospitalized specifically for ACS conditions (i.e. conditions that can be prevented with regular primary care in the community; Hand et al., 2019; Zerbo et al., 2018). These findings further suggest that primary care services may not be meeting autistic adults’ healthcare needs, leading to use of costly higher levels of care. We posit that this pattern may, in part, be related to factors such as providers’ lack of experience in providing healthcare for autistic adults (Unigwe et al., 2017), and resulting challenges with patient–provider communication and management of health conditions (Dern & Sappok, 2016; Raymaker et al., 2017).

Importantly, many kinds of preventive services are routinely provided during primary care visits (Dehmer, Maciosek, LaFrance, & Flottemesch, 2017; Kim et al., 2018) and have been shown to reduce the use of tertiary healthcare services (Centers for Disease Control and Prevention, 2019). It is encouraging that studies in this review found that autistic adults were more likely to receive most preventive services that were examined (Ames et al., 2021; Zerbo et al., 2018) including vaccinations (Ames et al., 2021; Nicolaidis et al., 2013) and various screening tests (Zerbo et al., 2018). However, a nuanced understanding of autistic adults’ preventive service use remains unclear since the studies we identified in this review focused on (1) preventive services received in exclusively primary care settings and (2) a limited number of preventive services. Some preventive services are provided routinely in multiple settings (e.g. mammography; Stanley et al., 2017) or in secondary healthcare settings (e.g. bone density tests; USPSTF, 2018) and, therefore, likely would not be fully captured in analyses that exclusively analyzed primary care claims data. In addition, while there are dozens of recommended preventive care services (USPSTF, 2021), the studies in this review focused on a relatively limited scope of services like vaccinations or cancer screenings. As such, we have an incomplete picture of autistic adults’ preventive care use. To better understand autistic adults’ preventive service use, it is important that future studies examine a wider array of preventive services delivered in a variety of settings. Encouragingly, recent evidence indicates that some primary care delivery models may increase receipt of dozens of preventive services among autistic adults (Hand et al., 2021). Such delivery models are critical to replicate as they may promote delivery of higher quality primary care for autistic adults and may reduce their use of tertiary healthcare services, particularly for health conditions that are sensitive to ambulatory and preventive care.

Outpatient mental healthcare and autistic adults’ use of tertiary health services

Good-quality studies consistently found that autistic adults used outpatient mental health services to a greater degree than comparison groups (Ames et al., 2021; Maddox et al., 2018; Zerbo et al., 2018). This pattern is unsurprising given autistic adults’ high prevalence of co-occurring mental health conditions (Lai et al., 2019). However, as with primary care, frequent receipt of outpatient mental healthcare services may indicate autistic adults’ access to care but not necessarily to mental healthcare that is high quality and that meets their needs. Inadequate mental healthcare, therefore, may also contribute to their frequent use of tertiary healthcare services for mental health conditions. Indeed, it is well-established that autistic adults are frequently hospitalized for mental health conditions as children and adults (Schlenz, Carpenter, Bradley, Charles, & Boan, 2015; Vohra et al., 2016; Weiss et al., 2018). Like in other service areas, a lack of providers trained to provide care for autistic adults is characteristic of the mental healthcare landscape (Maddox et al., 2020).

Future directions

The service patterns observed in this review underscore the nationally recognized need for more providers to be trained to provide care for autistic adults to promote high quality service delivery (IACC, 2017). Providers trained to provide care for autistic individuals are needed in all healthcare settings, and it is encouraging that providers from various settings, from primary care (Urbanowicz et al., 2020) to mental healthcare (Maddox et al., 2020), have expressed interest in such training. As the healthcare needs of autistic adults are further elucidated, the need for a healthcare workforce that is eager to learn to meet these needs is paramount to promote high-quality care and reduce autistic adults’ high likelihood of hospitalization and ED use.

Limitations

There are a number of limitations to our review that we would like to acknowledge. It is possible that our electronic database search strategy did not capture all published articles relevant to the review question. However, we did consult with a research librarian when developing our search strategy, which increases our confidence that our search strategy was thorough. Data from some included studies were as old as 2010, which may not offer an up-to-date picture of service use. Important sample demographic characteristics across studies (e.g. predominantly White participants) were likely not representative of the broader population of autistic adults, which limits the generalizability of our findings. Many other healthcare services could have been included in this review, which would have provided a more comprehensive picture of autistic adults’ service use patterns. The five services that were included in our review, however, are foundational healthcare services for adults regardless of autism status and are those that have been described most often in the available literature. It is, therefore, unlikely that the omission of other services detracts from the value of our findings. While some sources (e.g. unpublished, non-peer reviewed research, and research from countries other than the United States) could have contributed to our findings, we omitted these sources to focus on aggregation of peer-reviewed studies most relevant to the US healthcare system. Finally, our review offers a narrative synthesis as opposed to a meta-analysis. Given the relatively small number of studies included in most service areas, we feel that this was an appropriate approach to synthesis, still providing a valuable picture of autistic adults’ use of important health services.

Conclusion

This systematic review examined autistic adults’ use of five foundational healthcare services within the US healthcare system. Our findings indicate that autistic adults may be hospitalized, use outpatient mental health services, primary care, and preventive services to an equal or greater degree relative to adults from the general population and adults with ADHD. Autistic adults’ ED use may be equal or higher than adults from the general population as well. These findings highlight the immediate need for providers trained to care for autistic adults to be available in healthcare settings, as well as for current and future providers to be trained to care for this growing population. Future research should further examine the quality of primary and secondary healthcare services received by autistic adults and identify targets for improvement, which may ultimately reduce autistic adults’ frequent use of the ED and hospitalizations.

Supplemental Material

sj-docx-1-aut-10.1177_13623613211060906 – Supplemental material for Healthcare service use patterns among autistic adults: A systematic review with narrative synthesis

Supplemental material, sj-docx-1-aut-10.1177_13623613211060906 for Healthcare service use patterns among autistic adults: A systematic review with narrative synthesis by Daniel Gilmore, Morgan Krantz, Lindy Weaver and Brittany N Hand in Autism

Footnotes

Acknowledgements

The authors would like to thank Anna Biszaha, MLIS for her contributions to this work.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Community involvement statement

Autistic adults were not involved in this study.

ORCID iDs

Daniel Gilmore

Brittany N Hand

Supplemental material

Supplemental material for this article is available online.

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