Key Points
Question
Is diagnosis of autism spectrum disorder in childhood associated with educational attainment and employment?
Findings
In this cross-sectional study of 8910 individuals with and without autism spectrum disorder identified through population-based registers in Denmark, the proportion of those with autism spectrum disorder who completed compulsory primary and lower secondary education (ninth grade) was similar to that for individuals without autism spectrum disorder. At age 25 years, individuals with autism spectrum disorder had a lower prevalence of educational attainment beyond ninth grade and lower employment compared with those without autism spectrum disorder.
Meaning
This study’s findings indicated that a diagnosis of autism spectrum disorder was not associated with a lower prevalence of compulsory educational attainment but was associated with a lower prevalence of further educational attainment and employment.
Abstract
Importance
Population-based data on educational and employment outcomes in adulthood among individuals diagnosed with autism spectrum disorder (ASD) in childhood are currently limited.
Objective
To evaluate educational attainment and employment among individuals with and without a diagnosis of ASD before age 12 years in Denmark.
Design, Setting, and Participants
This nationwide cross-sectional prevalence study was conducted using data from Danish registers. Individuals with a diagnosis of ASD recorded before age 12 years were identified among all individuals born in Denmark between January 1, 1989, and December 31, 1991, who were alive at age 25 years. Individuals with ASD were then matched on a 10:1 ratio by age, sex, and region of residence with a comparison population of individuals without a diagnosis of ASD at age 12 years. Data were analyzed from March 2019 to December 2020.
Exposures
Autism spectrum disorder diagnosis and diagnostic subtype recorded before age 12 years.
Main Outcomes and Measures
Adjusted prevalence ratios (aPRs) with 95% CIs for the completion of compulsory primary and lower secondary school (grade 9), upper secondary school (grades 10-12 or vocational), and tertiary school (university) and for employment by age 25 years were estimated using log-binomial regression analysis.
Results
A total of 810 individuals with a diagnosis of ASD before age 12 years were matched with a comparison population of 8100 individuals without ASD. The prevalence of ninth-grade completion was similar among those with and without ASD (785 individuals [96.9%] and 7982 individuals [98.5%], respectively; aPR, 0.98; 95% CI, 0.97-1.00). Compared with those without ASD, persons with ASD had a lower prevalence of completing upper secondary school (6338 individuals [78.2%] vs 286 individuals [35.3%], respectively; aPR, 0.46; 95% CI, 0.42-0.50) and tertiary school (2185 individuals [27.0%] vs 70 individuals [8.6%]; aPR, 0.33; 95% CI, 0.26-0.41) and obtaining employment (4284 individuals [77.7%] vs 177 individuals [27.2%]; aPR, 0.35; 95% CI, 0.31-0.40) at age 25 years. A ninth-grade final examination score was available for 394 individuals (48.6%) with ASD and 7417 individuals (91.6%) without ASD. In an analysis stratified by ASD subtype, individuals diagnosed with childhood autism had lower educational attainment and employment than those diagnosed with Asperger syndrome or pervasive developmental disorder not otherwise specified. A total of 461 individuals (56.9%) with ASD were receiving public assistance or a pension (ie, disability benefits) at age 25 years compared with 1094 individuals (13.5%) without ASD in the comparison population.
Conclusions and Relevance
In this population-based cross-sectional study, a diagnosis of ASD in childhood was not associated with the completion of compulsory primary and lower secondary education (ninth grade). An ASD diagnosis before age 12 years was associated with a lower prevalence of attaining education beyond ninth grade and obtaining employment by age 25 years, indicating a substantially higher risk of reliance on public assistance in young adulthood.
This cross-sectional study uses data from national population-based registers to assess educational attainment and employment in young adulthood among individuals with and without a diagnosis of autism spectrum disorder before age 12 years in Denmark.
Introduction
Autism spectrum disorder (ASD) is a heritable condition comprising a broad range of disability levels from mild to severe and is characterized by deficits in social communication and unusually restricted repetitive behavior and interests. The worldwide prevalence of ASD is approximately 1%.1 Data regarding long-term educational attainment and employment among persons with ASD are sparse and often based on selected or small populations.
A 2016 systematic review and meta-analysis of overall outcomes among individuals with ASD identified 15 studies from the United Kingdom, Scandinavia, North America, and Japan, with a mean age at follow-up ranging from 12 to 44 years but comprising only 828 total individuals with ASD.2 The overall outcome of those with ASD was reported to be good (normal or near-normal social life and satisfactory functioning at school or work) for 20% of individuals, fair (social and educational progress despite social abnormalities) for 31% of individuals, and poor (severely impaired but with some potential for social progress) or very poor (unable to lead any kind of independent existence) for 48% of individuals.2 Another review reported considerable variability in school performance among persons with ASD.3
The largest US study of 500 individuals with ASD who were receiving special education services indicated that 35% had attended college and 55% had paid employment during the first 6 years after high school completion.4 A large Danish population-based study of children with mental disorders recently found that children with childhood autism or Asperger syndrome (2 diagnostic subtypes of ASD) completed the ninth-grade final examination at a lower proportion than children without mental disorders, and fewer children with childhood autism completed the final ninth-grade examination compared with children with Asperger syndrome.5 To extend the knowledge of educational and employment outcomes among young adults with ASD, we aimed to examine the association of ASD with educational attainment and employment in a population-based study of individuals with and without ASD in Denmark.
Methods
Study Design and Population
This cross-sectional prevalence study used routinely collected data from population-based nationwide registries in Denmark. Data were accessed via researcher services on Statistics Denmark. The study was registered at the Danish Data Protection Agency from Aarhus University and conducted in accordance with the Danish Act on Processing of Personal Data, which specifies that informed consent is not required for register-based studies in Denmark. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline for cross-sectional studies.
The study population comprised individuals in Denmark who were aged 12 years between January 1, 2001, and December 31, 2003 (born from January 1, 1989, to December 31, 1991), and who had a diagnosis of ASD recorded before age 12 years. A comparison group without an ASD diagnosis before age 12 years was obtained from the general Danish population6 and matched on a 10:1 ratio, with replacement,7 on birth year, sex, and region of residence with each person with an ASD diagnosis. Both groups were observed until age 25 years. We excluded individuals who died or emigrated before age 25 years and individuals who did not have information on mother, father, sex, or region of residence (additional inclusion and exclusion criteria are available in the eFigure in the Supplement).
Definitions, Outcomes, and Covariates
Autism spectrum disorder was defined as any ASD diagnosis recorded in the Danish Psychiatric Central Register8 using International Classification of Diseases, Eighth Revision (ICD-8) codes 299.00, 299.01, 299.02, and 299.03 for diagnoses before 1994 and International Classification of Diseases, Tenth Revision (ICD-10) codes F84.0, F84.1, F84.5, F84.8, and F84.9 for diagnoses in 1994 and later. The Danish Psychiatric Central Register includes discharge diagnoses from inpatient admissions through 1994 and from both inpatient and outpatient hospital encounters beginning in 1995. In the stratified analysis, ASD subtypes included childhood autism (ICD-8 code 299.00 and ICD-10 code F84.0), Asperger syndrome (ICD-8 code 299.02 and ICD-10 code F84.5), or pervasive developmental disorder not otherwise specified (ICD-8 codes 299.01 and 299.03 and ICD-10 codes F84.1, F84.8, and F84.9).
Educational attainment was classified according to the framework of the International Standard Classification of Education (ISCED), 2011 version.9 Data on educational attainment (yes or no) at age 25 years (2014-2016) were obtained from the Population Education Register of Denmark. Data were collected for the completion of 3 educational levels: compulsory primary and lower secondary school (grade 9; ISCED levels 1-2), upper secondary school (grades 10-12 or vocational; ISCED level 3), and tertiary school (university; ISCED levels ≥4).10 In addition, mean test scores at the end of ninth grade were obtained from the Danish Academic Achievement Register.
Five distinct categories were used for employment status: unemployed, student, receiving public assistance, employed, receiving a pension (ie, disability benefits), and self-employed (including working at spouse’s company). Employment at age 25 years was defined as having a paid job for more than 50% of the year (yes or no). Employment status was also categorized by skill level and skills specialization based on 1-digit codes from the Danish version of the International Standard Classification of Occupations published in 2008 (DISCO-08),11 via the Employment Classification Module.
The following covariates were assessed separately for parents of the study population: (1) age (in years) at the child’s birth (continuous variables), which was obtained from the Danish Civil Registration System; (2) recorded psychiatric disorders (schizophrenia, schizotypal, and delusional disorders; affective disorders; neurotic, stress-related, and somatoform disorders; disorders of adult personality and behavior; and ASD) that were diagnosed from 5 years before the child’s birth to the beginning of follow-up at the child’s twelfth birthday, which were obtained from the Danish Psychiatric Central Register (eTable 1 in the Supplement); and (3) socioeconomic status in the year before the child’s birth (representing prenatal exposure), defined by employment status and DISCO-08 job codes obtained from the Employment Classification Module.
Statistical Analysis
We selected potential confounding variables based on previously published data.12 Covariates associated with the outcomes were included to increase the precision of the estimates. In addition to an unadjusted model, we used a model adjusted for parental characteristics that included age, socioeconomic status, and psychiatric disorders.
Log-binomial regression analysis was used to estimate prevalence ratios (PRs) with 95% CIs (unadjusted and adjusted for the covariates) for educational level (completion of ninth grade, upper secondary, or tertiary education) and employment status (yes or no) among individuals with and without ASD. The ASD subtypes (childhood autism, Asperger syndrome, and pervasive developmental disorder not otherwise specified) were also compared.13 Students were excluded from the comparison of employment status because not all students had completed their educations by age 25 years. Supplementary analyses, stratified by sex and restricted to individuals without intellectual disabilities, were performed to obtain unadjusted results on educational attainment and employment for individuals with and without ASD. For some categories, exact numbers and percentages were not calculated per the Statistics Denmark requirement that exact counts not be reported for groups comprising less than 5 people.
Ordinal logistic regression analysis was used for calculating prevalence odds ratios for different levels of ninth-grade final examination scores among individuals with and without ASD and among the ASD subtypes, with the highest grade levels (10-12) used as the reference category. Hazard ratios (HRs) were calculated using Cox regression analysis to compare age (in years) at the completion of ninth grade with age (in years) at the completion of upper secondary school among individuals with and without ASD and among the ASD subtypes, adjusted for a similar set of covariates.14
Multinomial logistic regression analysis was used to calculate odds ratios comparing employment status and job types among individuals with and without ASD and among the ASD subtypes, with employed status and professional job type (DISCO-08 group 2) used as reference categories. Data were analyzed using SAS software, version 9.4 (SAS Institute), from March 2019 to December 2020.
Results
A total of 810 individuals with a diagnosis of ASD before age 12 years were matched with a comparison population of 8100 individuals (Table 1). Maternal and paternal age distributions and socioeconomic status were similar between the 2 groups. The mothers of individuals with ASD had a higher prevalence of psychiatric disorders compared with the mothers of those without ASD (eg, 63 mothers [7.8%] vs 274 mothers [3.4%] had neurotic, stress-related, or somatoform disorders, respectively) (Table 2). With regard to paternal mental disorders, the numbers were low, but no major differences were observed. A total of 785 individuals (96.9%) with ASD and 7982 individuals (98.5%) without ASD attained a ninth-grade education (adjusted PR [aPR], 0.98; 95% CI, 0.97-1.00) (Table 3). However, compared with individuals without ASD, those with ASD had a substantially lower prevalence of completing upper secondary school (6338 individuals [78.2%] vs 286 individuals [35.3%], respectively; aPR, 0.46; 95% CI, 0.42-0.50) and tertiary school (2185 individuals [27.0%] vs 70 individuals [8.6%]; aPR, 0.33; 95% CI, 0.26-0.41) and of obtaining employment (4284 individuals [77.7%] vs 177 individuals [27.2%]; aPR, 0.35; 95% CI, 0.31-0.40) by age 25 years.
Table 1. Characteristics of Individuals With ASD and Without ASD.
| Characteristic | No. (%) | |
|---|---|---|
| Individuals with ASD (n = 810) | Individuals without ASD (n = 8100) | |
| Calendar year of birth | ||
| 1989 | 217 (26.8) | 2170 (26.8) |
| 1990 | 276 (34.1) | 2760 (34.1) |
| 1991 | 317 (39.1) | 3170 (39.1) |
| Male sex | 702 (86.7) | 7020 (86.7) |
| Region of Denmark at birth | ||
| North Denmark Region | 81 (10.0) | 810 (10.0) |
| Central Denmark Region | 192 (23.7) | 1920 (23.7) |
| Region of Southern Denmark | 173 (21.4) | 1730 (21.4) |
| Region Zealand | 111 (13.7) | 1110 (13.7) |
| Capital Region of Denmark | 253 (31.2) | 2530 (31.2) |
Abbreviation: ASD, autism spectrum disorder.
Table 2. Characteristics of Parents of Individuals With and Without Autism Spectrum Disorder.
| Characteristic | No. (%) | |
|---|---|---|
| Individuals with ASD (n = 810) | Individuals without ASD (n = 8100) | |
| Maternala | ||
| Age at child’s birth, y | ||
| <25 | 208 (25.7) | 1926 (23.8) |
| 25–29 | 338 (41.7) | 3413 (42.1) |
| 30–34 | 186 (23.0) | 2031 (25.1) |
| 35–39 | 68 (8.4) | 632 (7.8) |
| >39 | 10 (1.2) | 98 (1.2) |
| Mental disorders | ||
| Schizophrenia, schizotypal, and delusional | 11 (1.4) | 43 (0.5) |
| Affective | 24 (3.0) | 138 (1.7) |
| Neurotic, stress-related, and somatoform | 63 (7.8) | 274 (3.4) |
| Adult personality and behavior | 25 (3.1) | 132 (1.6) |
| Autism spectrum | <5 (NE)b | <5 (NE)b |
| Socioeconomic status in year before child’s birth | ||
| Unemployed | 54 (6.7) | 505 (6.2) |
| Student | 42 (5.2) | 295 (3.6) |
| Receiving public assistance or missing informationc | 47 (5.8) | 443 (5.5) |
| Employed | 605 (74.7) | 6234 (77.0) |
| Receiving a pension | 9 (1.1) | 40 (0.5) |
| Self-employed or working at spouse’s company | 53 (6.5) | 583 (7.2) |
| Paternala | ||
| Age at child’s birth, y | ||
| <25 | 95 (11.7) | 974 (12.0) |
| 25–29 | 265 (32.7) | 2794 (34.5) |
| 30–34 | 245 (30.2) | 2487 (30.7) |
| 35–39 | 132 (16.3) | 1266 (15.6) |
| >39 | 73 (9.0) | 579 (7.1) |
| Mental disorders | ||
| Schizophrenia, schizotypal, and delusional | 9 (1.1) | 51 (0.6) |
| Affective | 7 (0.9) | 90 (1.1) |
| Neurotic, stress-related, and somatoform | 27 (3.3) | 164 (2.0) |
| Adult personality and behavior | 14 (1.7) | 68 (0.8) |
| Autism spectrum | 0 | 0 |
Abbreviations: ASD, autism spectrum disorder; NE, not estimated.
Diagnosed from 5 years before child’s birth until child’s 12th birthday. Specific diagnostic codes are available in eTable 1 in the Supplement.
Statistics Denmark prohibits the reporting of exact counts for groups comprising fewer than 5 individuals.
Categories were combined because of the low number of individuals (<5) in 1 category.
Table 3. Educational Attainment and Employment at Age 25 Years Among Individuals With and Without Autism Spectrum Disorder.
| Level | No./total No. (%) | Prevalence ratio (95% CI) | ||||
|---|---|---|---|---|---|---|
| Individuals with ASD (n = 810) | Individuals without ASD (n = 8100) | |||||
| Unadjusted | Adjusteda | |||||
| Attained | Not attained | Attained | Not attained | |||
| All ASD diagnoses | ||||||
| Educational level | ||||||
| Primary and lower secondary (grade 9) | 785/810 (96.9) | 25/810 (3.1) | 7982/8100 (98.5) | 118/8100 (1.5) | 0.98 (0.97-1.00) | 0.98 (0.97-1.00) |
| Upper secondary (grades 10-12 or vocational)b | 286/810 (35.3) | 524/810 (64.7) | 6338/8100 (78.2) | 1762/8100 (21.8) | 0.45 (0.41-0.50) | 0.46 (0.42-0.50) |
| Tertiary (university)b | 70/810 (8.6) | 740/810 (91.4) | 2185/8100 (27.0) | 5915/8100 (73.0) | 0.32 (0.26-0.40) | 0.33 (0.26-0.41) |
| Employment >50% of yearc | 177/650 (27.2) | 473/650 (72.8) | 4284/5517 (77.7) | 1233/5517 (22.3) | 0.35 (0.31-0.40) | 0.35 (0.31-0.40) |
| Childhood autism | ||||||
| Educational level | ||||||
| Primary and lower secondary (grade 9) | 142 (97.0)d | <5 (3.0)d | 1441/1460 (98.7) | 19/1460 (1.3) | 0.99 (0.96-1.01) | 0.99 (0.96-1.02) |
| Upper secondary (grades 10-12 or vocational)b | 21/146 (14.4) | 125/146 (85.6) | 1153/1460 (79.0) | 307/1460 (21.0) | 0.18 (0.12-0.27) | 0.18 (0.12-0.27) |
| Tertiary (university)b | <5 (3.0)d | 142 (97.0)d | 385/1460 (26.4) | 1075/1460 (73.6) | 0.10 (0.04-0.27) | NE |
| Employment >50% of yearc | 10/126 (7.9) | 116/126 (92.1) | 775/997 (77.7) | 222/997 (22.3) | 0.10 (0.06-0.19) | NE |
| Asperger syndrome | ||||||
| Educational level | ||||||
| Primary and lower secondary (grade 9) | 241/249 (96.8) | 8/249 (3.2) | 2457/2490 (98.7) | 33/2490 (1.3) | 0.98 (0.96-1.00) | 0.98 (0.96-1.00) |
| Upper secondary (grades 10-12 or vocational)b | 130/249 (52.2) | 119/249 (47.8) | 1947/2490 (78.2) | 543/2490 (21.8) | 0.67 (0.59-0.75) | 0.66 (0.59-0.75) |
| Tertiary (university)b | 37/249 (14.9) | 212/249 (85.1) | 651/2490 (26.1) | 1839/2490 (73.9) | 0.57 (0.42-0.77) | NE |
| Employment >50% of yearc | 57/172 (33.1) | 115/172 (66.9) | 1340/1697 (79.0) | 357/1697 (21.0) | 0.42 (0.34-0.52) | 0.42 (0.34-0.52) |
| PDD-NOS | ||||||
| Educational level | ||||||
| Primary and lower secondary (grade 9) | 402/415 (96.9) | 13/415 (3.1) | 4084/4150 (98.4) | 66/4150 (1.6) | 0.98 (0.97-1.00) | 0.98 (0.97-1.00) |
| Upper secondary (grades 10-12 or vocational)b | 135/415 (32.5) | 280/415 (17.5) | 3238/4150 (78.0) | 912/4150 (22.0) | 0.42 (0.36-0.48) | 0.43 (0.37-0.49) |
| Tertiary (university)b | 29/415 (7.0) | 386/415 (93.0) | 1149/4150 (27.7) | 3001/4150 (72.3) | 0.25 (0.18-0.36) | 0.26 (0.19-0.37) |
| Employment >50% of yearc | 110/352 (31.2) | 242/352 (68.8) | 2169/2823 (76.8) | 654/2823 (23.2) | 0.41 (0.35-0.48) | 0.41 (0.35-0.48) |
Abbreviations: ASD, autism spectrum disorder; NE, not estimated because of small number of individuals; PDD-NOS, pervasive developmental disorder not otherwise specified.
Adjusted for parental characteristics, which included age, socioeconomic status, and mental disorders (excluding parental diagnosis of autism spectrum disorder because counts were too low to include in calculations).
Calculated based on all individuals in the category without requiring attainment of previous educational level.
Individuals who were students at age 25 years were not included in calculations.
Statistics Denmark prohibits the reporting of exact counts for groups comprising fewer than 5 individuals; therefore, denominators were not reported, and percentages were rounded.
The analysis stratified by ASD subtype indicated that individuals diagnosed with childhood autism had a lower prevalence of educational attainment after ninth grade (eg, 21 individuals [14.4%] completed upper secondary school; aPR, 0.18; 95% CI, 0.12-0.27) and a lower prevalence of employment (10 individuals [7.9%] were employed >50% of the year; aPR, not estimated because of small numbers) compared with individuals with Asperger syndrome (eg, 130 individuals [52.2%] completed upper secondary school [aPR, 0.66; 95% CI, 0.59-0.75], and 57 individuals [33.1%] were employed >50% of the year [aPR, 0.42; 95% CI, 0.34-0.52]) and pervasive developmental disorder not otherwise specified (eg, 135 individuals [32.5%] completed upper secondary school [aPR, 0.43; 95% CI, 0.37-0.49], and 110 individuals [31.2%] were employed >50% of the year [aPR, 0.41; 95% CI, 0.35-0.48]). Unadjusted analyses, stratified by sex, among individuals with and without ASD indicated higher PRs for upper secondary and tertiary educational attainment and employment among men compared with women (eTable 2 in the Supplement). When restricted to individuals without intellectual disabilities, those with ASD were more likely to complete their educations and obtain a job (eTable 2 in the Supplement) than those in the nonrestricted comparison (Table 3).
A total of 394 individuals (48.6%) with ASD and 7417 individuals (91.6%) without ASD completed the ninth-grade final examination. However, fewer than 27.0% of individuals with childhood autism completed the test. Among those with available data on final test scores, a larger proportion of individuals with ASD achieved higher scores than those without ASD (eTable 3 in the Supplement). The stratified analyses of ASD subtypes indicated that individuals with Asperger syndrome had the highest ninth-grade final examination scores.
The median difference in age at completion of ninth grade between individuals with and without ASD was 0.3 years (among those with ASD, median age, 15.3 years; interquartile range [IQR], 14.8-16.0 years; among those without ASD, median age, 15.1 years; IQR, 14.8-15.4 years) (Table 4). For completion of upper secondary education, the difference was more substantial, with a median difference of 1.1 years between individuals with ASD (median age, 21.3 years; IQR, 20.1-22.8 years) and without ASD (median age, 20.2 years; IQR, 19.5-21.3 years). The median difference in time to obtain employment after the completion of education was small. No substantial differences were observed between ASD subtypes, although this finding was based on small numbers.
Table 4. Age at Completion of Ninth Grade and Upper Secondary School and Time to Employment Among Individuals With and Without Autism Spectrum Disorder.
| Variable | Median (IQR) | HR (95% CI) per y | ||
|---|---|---|---|---|
| Individuals with ASDa | Individuals without ASDa | Unadjusted | Adjustedb | |
| All ASD diagnoses | ||||
| Age at completion, y | ||||
| Ninth grade | 15.3 (14.8-16.0) | 15.1 (14.8-15.4) | 0.60 (0.56-0.65) | 0.60 (0.55-0.64) |
| Upper secondary school | 21.3 (20.1-22.8) | 20.2 (19.5-21.3) | 0.28 (0.25-0.31) | 0.27 (0.24-0.31) |
| Time from school completion to employment, y | 0.1 (0.0-1.7) | 0 (0-0.2) | NA | NA |
| Childhood autism | ||||
| Age at completion, y | ||||
| Ninth grade | 15.1 (14.7-15.6) | 15.1 (14.8-15.4) | 0.74 (0.62-0.88) | 0.72 (0.60-0.86) |
| Upper secondary school | 21.2 (19.8-22.1) | 20.1 (19.5-21.3) | 0.10 (0.07-0.16) | 0.10 (0.07-0.15) |
| Time from school completion to employment, y | 1.2 (0.8-2.6) | 0 (0-0.2) | NA | NA |
| Asperger syndrome | ||||
| Age at completion, y | ||||
| Ninth grade | 15.4 (14.9-16.0) | 15.1 (14.8-15.4) | 0.56 (0.49-0.64) | 0.55 (0.48-0.63) |
| Upper secondary school | 21.0 (19.9-22.7) | 20.2 (19.5-21.3) | 0.47 (0.39-0.56) | 0.45 (0.37-0.53) |
| Time from school completion to employment, y | 0.1 (0-2.0) | 0 (0-0.2) | NA | NA |
| PDD-NOS | ||||
| Age at completion, y | ||||
| Ninth grade | 15.3 (14.9-16.0) | 15.1 (14.8-15.4) | 0.59 (0.53-0.66) | 0.59 (0.53-0.66) |
| Upper secondary school | 21.8 (20.2-23.0) | 20.1 (19.4-21.2) | 0.25 (0.21-0.30) | 0.25 (0.21-0.30) |
| Time from school completion to employment, y | 0 (0-1.5) | 0 (0-0.3) | NA | NA |
Abbreviations: ASD, autism spectrum disorder; HR, hazard ratio; IQR, interquartile range; NA, not applicable; PDD-NOS, pervasive developmental disorder not otherwise specified.
Among those who completed the specified educational level or obtained employment.
Adjusted for parental characteristics, which included age, socioeconomic status, and history of mental disorders (excluding parental diagnosis of autism spectrum disorder because counts were too low to include in calculations).
The prevalence of receiving a pension or other type of public assistance was higher among persons with ASD (461 individuals [56.9%]) compared with those without ASD (1094 individuals [13.5%]) (Table 5). The prevalence of employment by age 25 years was lower among individuals with ASD (177 individuals [21.9%]) compared with those without ASD (4284 individuals [52.9%]). Among those employed, a higher proportion of individuals with ASD vs without ASD were working as technicians or associate professionals (DISCO-08 group 3)11 or as plant or machine operators and assemblers (DISCO-08 group 8) relative to professionals (DISCO-08 group 2); however, the numbers were small and the estimates imprecise (Table 4).
Table 5. Employment Status and Job Types at Age 25 Years Among Individuals With and Without Autism Spectrum Disorder.
| Variable | No./total No. (%) | Odds ratio (95% CI) | ||
|---|---|---|---|---|
| Individuals with ASD (n = 810) | Individuals without ASD (n = 8100) | Unadjusted | Adjusteda | |
| Employment status | ||||
| Unemployed | 12/810 (1.5) | 139/8100 (1.7) | 2.09 (1.14-3.84) | 2.11 (1.14-3.88) |
| Student | 160/810 (19.8) | 2583/8100 (31.9) | 1.50 (1.20-1.87) | 1.49 (1.19-1.86) |
| Receiving public assistance | 173/810 (21.4) | 865/8100 (10.7) | 4.84 (3.88-6.04) | 5.09 (4.06-6.38) |
| Employed | 177/810 (21.9) | 4284/8100 (52.9) | 1 [Reference] | 1 [Reference] |
| Receiving a pension or missing informationb | 288/810 (35.6) | 229/8100 (2.8) | 30.44 (24.19-38.30) | 34.24 (26.98-43.46) |
| Job typec | ||||
| Professional | 18/177 (10.2) | 578/4284 (13.5) | 1 [Reference] | 1 [Reference] |
| Technician or associate professional | 16/177 (9.0) | 308/4284 (7.2) | 1.67 (0.84-3.32) | 1.70 (0.85-3.40) |
| Service or sales | 38/177 (21.5) | 808/4284 (18.9) | 1.51 (0.85-2.67) | 1.58 (0.89-2.80) |
| Clerical support | 14/177 (7.9) | 324/4284 (7.6) | 1.39 (0.68-2.83) | 1.45 (0.71-2.96) |
| Craft or related trade | 25/177 (14.1) | 928/4284 (21.7) | 0.87 (0.47-1.60) | 0.89 (0.48-1.65) |
| Plant or machine operator/assembler | 20/177 (11.3) | 206/4284 (4.8) | 3.12 (1.62-6.02) | 3.35 (1.72-6.51) |
| Elementaryd | 19/177 (10.7) | 330/4284 (7.7) | 1.85 (0.96-3.57) | 1.93 (0.99-3.77) |
| Agriculture, forestry, and fishery; armed forces; or unspecified | 27/177 (15.3) | 802/4284 (18.7) | 1.08 (0.59-1.98) | 1.12 (0.61-2.07) |
Abbreviation: ASD, autism spectrum disorder.
Adjusted for parental characteristics, which included age, socioeconomic status, and history of mental disorders (excluding parental diagnosis of autism spectrum disorder because numbers were too low to include in calculations).
Data were combined because of low counts (<5 individuals) in each category.
Estimated for employed individuals only. Job types were based on the 1-digit Danish version of codes from the International Standard Classification of Occupations, 2008 (DISCO-08).
The International Standard Classification of Occupations defines elementary occupations as those comprising routine tasks that require the use of handheld tools and some physical effort.11
Discussion
This population-based cross-sectional study examined educational attainment and employment among young adults diagnosed with ASD before age 12 years. The prevalence of ninth-grade completion was similar between individuals with and without ASD, but a substantially lower proportion of persons with ASD completed the ninth-grade final examination. The prevalence of upper secondary and tertiary educational attainment and employment at age 25 years was more than 50% lower among individuals with ASD, with longer median educational completion times, compared with individuals without ASD.
Another recent Danish study found lower ninth-grade examination scores among children with childhood autism but no association among children with Asperger syndrome,5 suggesting that those with childhood autism perform worse in primary and lower secondary school. The results of the present study indicate that it may be more difficult for individuals with ASD to attain education after completing compulsory primary and lower secondary school, and individuals with childhood autism appear to attain additional education and obtain employment at substantially lower rates than those with other ASD subtypes.
Information on educational attainment and employment in adulthood among individuals with ASD has been previously assessed in a few selected study populations.15,16 In the largest previous study conducted in the US,4 the proportion of individuals with ASD who attended college was similar to that of the present study, with 35.3% of individuals completing upper secondary school. However, we found that only 27.2% of individuals with ASD were employed for more than 50% of the year by age 25 years, which is lower than the 55% of individuals who had paid employment during the first 6 years after high school in the previous study.4 Differences in inclusion criteria between the US study and the present study (the US study included only individuals receiving special education, and the present study included all individuals with an ASD diagnosis) and differences in the availability of public assistance between the US and Denmark may partially explain the difference in results. A majority of individuals with ASD (56.9%) were receiving public assistance or a pension at age 25 years compared with 13.5% of those in the comparison population. Several intervention programs have been initiated to help individuals with ASD improve their skills for educational and employment functioning, but these programs have had limited success to date.17
Limitations
This study has several limitations. The study was restricted to persons born in Denmark who were alive at age 25 years. Mortality may be slightly higher among individuals with ASD compared with the general population because of an increased risk of suicide among those with ASD.18 In addition, this study excluded emigrants and immigrants because of incomplete medical histories, which could have slightly biased our results. In Denmark, health care and education, including university education, is publicly funded; therefore, economic barriers are limited. Some misclassification or underreporting of ASD diagnosis may have occurred, given that we excluded diagnoses after age 12 years to ensure that the ASD diagnosis was present before the examined outcomes, and girls often receive ASD diagnoses at older ages. The examined outcomes and covariates in the Danish registers may also have been misclassified, but this is unlikely to produce differential misclassification.
The number of individuals identified with ASD in this study was similar to the number expected based on national prevalence rates of ASD in Denmark.19 A systematic review including 25 studies of 2022 individuals with ASD, with follow-up on adult cognitive, social, and behavioral outcomes among those with an ASD diagnosis before age 16 years, reported that ASD was generally persistent from childhood to adulthood; however, the severity of autism-associated behavioral symptoms generally improved in adulthood.20 We did not follow up on ASD diagnosis in our study, but it can be assumed that ASD is persistent into adulthood. The Population Education Register contains information on the highest completed educational level for 97% of the Danish population born between 1945 and 1990, and Statistics Denmark reports 0% to 3% misclassification in the register.10 The validity of the Employment Classification Module is also considered high.21 Childhood autism among Danish children born between 1990 and 1999 has previously been validated, with a positive predictive value of 94% based on medical records review of 499 cases22; however, overall ASD has not, to our knowledge, been validated.
The study population was limited to Danish children born from January 1989 through December 1991. Although the study’s findings may not be representative of other time periods and countries, scientific conclusions based on studies with limited variability in confounding factors are considered more valid than those based on studies with a highly representative sample but greater variability in confounding factors.23
Conclusions
In Denmark, a diagnosis of ASD before age 12 years was not associated with the prevalence of compulsory primary and lower secondary (ninth grade) educational attainment but was associated with a lower prevalence of completing ninth-grade final examinations. Persons diagnosed with childhood autism also had a substantially lower prevalence of educational attainment beyond ninth grade and a lower prevalence of employment by age 25 years, with more than 50% of individuals with ASD dependent on some type of public assistance in young adulthood.
eFigure. Flowchart of Inclusions and Exclusions for Individuals in the Study
eTable 1. ICD-10 and ICD-8 Diagnostic Codes Used to Identify Maternal and Paternal Mental Disorders
eTable 2. School and Job Attainment for More Than 50% of the Year at Age 25 Years Among Individuals With and Without ASD Stratified by Sex and Intellectual Disability
eTable 3. Average Marks Obtained on Ninth-Grade Final Tests for Students With Final Marks Among Individuals With and Without ASD
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Associated Data
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Supplementary Materials
eFigure. Flowchart of Inclusions and Exclusions for Individuals in the Study
eTable 1. ICD-10 and ICD-8 Diagnostic Codes Used to Identify Maternal and Paternal Mental Disorders
eTable 2. School and Job Attainment for More Than 50% of the Year at Age 25 Years Among Individuals With and Without ASD Stratified by Sex and Intellectual Disability
eTable 3. Average Marks Obtained on Ninth-Grade Final Tests for Students With Final Marks Among Individuals With and Without ASD