Diagnostic Overshadowing: When Words Fail Us

While last week’s witless analysis of Andrew Jackson’s life and presidency was great fun, today I am sticking to more serious issues on which I am far more proficient.  I am back in focus and prepared to discuss a very important research article which I expect to cite frequently in the future:1

Croen, L. A., et al. (2015). "The health status of adults on the autism spectrum." Autism 19(7): 814-823.

What is so significant about this article?  Simply put, it is one of very few published pieces that spells out what we already know.  Most of those who work with adults on the spectrum appreciate that the health status of this cohort is significantly compromised when compared to the general population.  Despite this, however, there have been very few studies to explicitly state this with expansive detail. This article offers just that. 

The study provides an analysis of the medical records for 1,507 adults with autism for services they received from Kaiser Permanente between January 2008 and December 2012 in northern California.  These individuals, ranging in age from 18 to 65+, were matched against a neurotypical control group for comparative analysis.  The average age of the cohort was 29 years of age; 65.6% were white, with 3.9% Hispanic, and 7.6% black.  Not surprisingly given the gender driven nature of this condition, 73% of the survey were males. 

Autism-related diagnoses among the participants were varied though 37.2% were listed as autistic disorder, 29.7% as Asperger’s, and 30.7% were listed under a diagnosis of PDD-NOS.  Just a reminder:  all of these autism subtypes are now subsumed under the title of Autism Spectrum Disorder (ASD).  Only 19.2% of those in the study had comorbid Intellectual Disability but ID is not something that is typically screened for (or formally diagnosed) in the KP protocol and is, therefore, likely to be significantly under-represented.

So what were the conclusions of this study?  The most common comorbidity was psychiatric conditions including anxiety (29%), bipolar disorder (11%), depression (26%), OCD (8%) and schizophrenia (8%).  The authors concluded that when adjusted for sex, age and ethnicity, adults with autism suffered depression at 2.9 times the rate of the control group and schizophrenia at 22 times the norm.  It should also be noted that women with autism had higher rates across the board for all psychiatric conditions with the exception of OCD and ADD.

As for other comorbid conditions?  The paper reports: “Nearly all major chronic medical conditions were significantly more common in adults with ASD than controls.” The most substantial differences between the subject and control group were found to be autoimmune conditions (13.9% among ASD vs 10.8% among controls), GI disorders (34.7% vs 27.5%), sleep disorders (17.6% vs 9.6%), and seizures (11.9% vs 0.73%).  Dyslipidemia was found at 22.8% in the ASD cohort (15.1% control), while diabetes was seen in 7.6% (with the control group at 4.3%). 

Rates of obesity were higher among those with autism (33.9% vs 27.0% for the control), which has been previously demonstrated in a wide range of studies.2-19  Once again females had higher rates across the board for all conditions, with the exception of GI disorders and some autoimmune diseases.

One of the most notable findings of the paper was the fact that suicide among the ASD cohort was found at a fivefold higher rate than the control group.  Moreover, half of the individuals who had attempted suicide did not have a comorbid diagnosis of depression, suggesting to the authors that significant under-diagnosis was likely.  This alarming trend has been noted elsewhere.20

As is often the case, the most interesting part of this paper was what it did not discuss, rather than what it revealed.  That is, how effective are medical systems at tracking and treatment of health related conditions among a population with verbal incapacity? 

Take suicide as an example.  The ability to determine suicidal ideation requires that a patient have a perspective: “To have a perspective, one needs language. To have a perspective means to formulate an individual vision, opinion or narrative about the world that represents your experiences. Consequently, if you cannot speak or fill out questionnaires, you cannot produce a perspective” 21. 

“To have a perspective, one needs language. To have a perspective means to formulate an individual vision, opinion or narrative about the world that represents your experiences. Consequently, if you cannot speak or fill out questionnaires, you cannot produce a perspective” 21. 

This is the very reason why so much of autism related research has focused on the high functioning end of the spectrum creating a “disquieting research trend" 22 in disability studies that emphasizes those who can speak.  At present there is neither a consensus nor a discussion as to whether studies addressing high functioning individuals are applicable to those with lower levels of communicative ability.

How would doctors even ascertain depression in a nonverbal patient?  But then again, how effective are they at tracking any medical condition given current practices and procedures?  For example, if a doctor does not specifically run diagnostic tests for metabolic markers, how would they be led to diabetes?  Doctors rely on patients to report symptoms but individuals who cannot verbalize have no ability to describe the typical symptoms of diabetes including excessive thirst or urination, fatigue, weight loss, and blurred vision.  Consequently, I hypothesize that under-diagnosis of many conditions is significant and widespread across the spectrum.

This references what is termed diagnostic overshadowing in autism, or the difficulty with finding underlying medical conditions given the limitations of communication and the highly heterogeneous nature of this population.  This is a very real handicap in providing adequate healthcare for this population and a topic that I will return to often.

References Cited

1. Croen LA, Zerbo O, Qian YG, et al. The health status of adults on the autism spectrum. Autism : the international journal of research and practice. 2015;19(7):814-823.
2. Gravestock S. Eating disorders in adults with intellectual disability. Journal of Intellectual Disability Research. 2000;44:625-637.
3. Memari A, Ziaee V, Mirfazeli F, Kordi R. Investigation of autism comorbidities and associations in a school-based community sample. Journal of child and adolescent psychiatric nursing : official publication of the Association of Child and Adolescent Psychiatric Nurses, Inc. 2012;25(2):84-90.
4. Henderson CM, Robinson LM, Davidson PW, Haveman M, Janicki MP, Albertini G. Overweight Status, Obesity, and Risk Factors for Coronary Heart Disease in Adults With Intellectual Disability. Journal of Policy and Practice in Intellectual Disabilities. 2008;5(3):174-177.
5. Rimmer JH, Yamaki K, Lowry BM, Wang E, Vogel LC. Obesity and obesity-related secondary conditions in adolescents with intellectual/developmental disabilities. Journal of intellectual disability research : JIDR. 2010;54(9):787-794.
6. Bandini LG, Curtin C, Hamad C, Tybor DJ, Must A. Prevalence of overweight in children with developmental disorders in the continuous national health and nutrition examination survey (NHANES) 1999-2002. J Pediatr. 2005;146(6):738-743.
7. De S, Small J, Baur LA. Overweight and obesity among children with developmental disabilities. Journal of intellectual & developmental disability. 2008;33(1):43-47.
8. Ells LJ, Lang R, Shield JP, et al. Obesity and disability - a short review. Obesity reviews : an official journal of the International Association for the Study of Obesity. 2006;7(4):341-345.
9. Stewart L, Van de Ven L, Katsarou V, et al. High prevalence of obesity in ambulatory children and adolescents with intellectual disability. Journal of intellectual disability research : JIDR. 2009;53(10):882-886.
10. Marshall D, McConkey R, Moore G. Obesity in people with intellectual disabilities: the impact of nurse-led health screenings and health promotion activities. Journal of advanced nursing. 2003;41(2):147-153.
11. Melville CA, Cooper SA, Morrison J, Allan L, Smiley E, Williamson A. The prevalence and determinants of obesity in adults with intellectual disabilities. Journal of Applied Research in Intellectual Disabilities. 2008;21(5):425-437.
12. Temple VA, Foley JT, Lloyd M. Body mass index of adults with intellectual disability participating in Special Olympics by world region. Journal of intellectual disability research : JIDR. 2013.
13. de Winter CF, Bastiaanse LP, Hilgenkamp TIM, Evenhuis HM, Echteld MA. Overweight and obesity in older people with intellectual disability. Research in developmental disabilities. 2012;33(2):398-405.
14. Janicki MP, Davidson PW, Henderson CM, et al. Health characteristics and health services utilization in older adults with intellectual disability living in community residences. Journal of Intellectual Disability Research. 2002;46:287-298.
15. Robertson J, Emerson E, Gregory N, et al. Lifestyle related risk factors for poor health in residential settings for people with intellectual disabilities. Research in developmental disabilities. 2000;21(6):469-486.
16. McGuire BE, Daly P, Smyth F. Lifestyle and health behaviours of adults with an intellectual disability. Journal of Intellectual Disability Research. 2007;51:497-510.
17. Moore KA, McGillivray J, Illingworth K, Brookhouse P. An investigation into the incidence of obesity and underweight among adults with an intellectual disability in an Australian sample. Journal of intellectual & developmental disability. 2004;29(4):306-318.
18. Stedman KV, Leland LS. Obesity and intellectual disability in New Zealand. Journal of intellectual & developmental disability. 2010;35(2):112-115.
19. Maaskant MA, van Knijff-Raeven AGM, Lantman-de Valk H, Veenstra MY. Weight Status of Persons with Intellectual Disabilities. Journal of Applied Research in Intellectual Disabilities. 2009;22(5):426-432.
20. Hirvikoski T, Mittendorfer-Rutz E, Boman M, Larsson H, Lichtenstein P, Bolte S. Premature mortality in autism spectrum disorder. The British journal of psychiatry : the journal of mental science. 2016;208(3):232-238.
21. Pols J. Enacting appreciations: Beyond the patient perspective. Health Care Analysis. 2005;13(3):203-221.
22. Dykens EM, Lense M. Intellectual Disabilities and Autism Spectrum Disorder: A Cautionary Note. In: Amaral D, Dawson G, Geschwind DH, eds. Autism spectrum disorders. New York: Oxford University Press; 2011:263-269.