Autoimmune disease risk and eating disorders

"We were set up. The cops were waiting for us."

"We observed an association between eating disorders and several autoimmune diseases with different genetic backgrounds. Our findings support the link between immune-mediated mechanisms and development of eating disorders".

So said the paper by Anu Raevuori and colleagues [1] (open-access) based on an analysis of over 2300 people "treated at the Eating Disorder Unit of Helsinki University Central Hospital between 1995 and 2010" compared with nearly 10,000 control participants (so yes, this was quite a well-powered study).

The Raevuori paper is open-access but if you want a few choice details, here goes...

• Based on a body of research literature looking at a possible association between eating disorders and autoimmune conditions like type 1 diabetes [2], authors set about testing the hypothesis on a large scale on whether "the risk of autoimmune diseases would be increased in individuals with eating disorders both prior and after the onset of the treatment for an eating disorder".
• Having already mentioned how large a scale the authors' participants groups were, various eating disorder diagnoses were confirmed based on ICD-10 criteria [3] and both research and control populations were assessed for some 30 autoimmune conditions based on existing hospital discharge registry. "Period and lifetime prevalences" were calculated from the data. 
• Results: "Participants with BN [bulimia nervosa] made up the largest patient group (54.0%), followed by those with AN [anorexia nervosa] (38.8%), and those with BED [binge eating disorder] (7.3%)". Over 5% of those diagnosed with an eating disorder had been diagnosed with one or more autoimmune conditions compared with just under 3% of controls when it came to looking at period prevalence (at the onset of treatment). Long quote coming up... "The risk of prior diagnosis of endocrinological autoimmune diseases (OR 3.3, 95% CI 2.4–4.6, P<0.001), of gastroenterological immune-mediated diseases (OR 2.0, 95% CI 1.3–3.1, P = 0.002), and of autoimmune diseases combined (OR 2.1 95% CI 1.7–2.7, P<0.001) was significantly higher among patients than among matched controls".
• With regards to lifetime prevalence (over the whole study period) "8.9% (N = 209) of patients and 5.4% of control individuals (N = 509) had ever been diagnosed with one or more autoimmune disease". 

Whilst only looking like a relatively small percentage difference in the rates of autoimmune conditions between the groups, it is the scale of the Raevuori study in terms of participant numbers which gives the data some 'edge'. As the authors also note, their use of the category BED - binge eating disorder - is also another plus to their study given it's recent inclusion into DSM-5 (see here).

As I always seem to be about papers mentioned on this blog, I was really quite interested in the results presented by Raevuori et al and their potential implications for how we describe eating disorders and the potential mechanisms involved in onset. Research into autoimmune conditions has recently been producing some rather important associations as per my covering of things like a [possible] link between autoimmune disorders following trauma and PTSD (see here) and even a suggested connection with some epilepsy (see here).

Raevuori and colleagues discuss several pertinent mechanisms potentially linking their findings including the ever-present issue of inflammation and: "Pro-inflammatory cytokines and antibodies/autoantibodies against neuronal antigens". They also mention some possible role for "intestinal microflora contributing to the development of cross-reactive neuronal autoantibodies [providing] a link between gut and brain" and the growing fascination with all-things gut microbiome. Their finding of a greater frequency of the inflammatory bowel disease (IBD), Crohn's disease in their eating disorder cohort offers some evidence for this assertion as a function of the growing interest in gut bacteria and IBDs [4].

Without hopefully going too far off tangent from the Raevuori paper, I started to think about how these results might also fit in with some of the research done on autism and whether there may be a bigger picture here. Eating disorders have been mentioned alongside the label autism quite a few times in the research literature [5]. My previous discussions on signs of autism in cases of eating disorders (see here) is one example. Likewise, autoimmune conditions and autism also seem to have something of a connection (see here) alongside presented data on markers of autoimmunity in cases of autism (see here and see here). One can perhaps see how the various elements - immune function, inflammation, gut bacteria, gut permeability? - might be intertwined, albeit in a rather complex fashion...?

Music then, and Naive by The Kooks.

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[1] Raevuori A. et al. The increased risk for autoimmune diseases in patients with eating disorders. PLoS One. 2014 Aug 22;9(8):e104845.

[2] Young V. et al. Eating problems in adolescents with Type 1 diabetes: a systematic review with meta-analysis. Diabet Med. 2013 Feb;30(2):189-98.

[3] Herpetz S. et al. The Diagnosis and Treatment of Eating Disorders. Dtsch Arztebl Int. Oct 2011; 108(40): 678–685.

[4] Manichanh C. et al. The gut microbiota in IBD. Nat Rev Gastroenterol Hepatol. 2012 Oct;9(10):599-608.

[5] Huke V. et al. Autism spectrum disorders in eating disorder populations: a systematic review. Eur Eat Disord Rev. 2013 Sep;21(5):345-51.

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Raevuori A, Haukka J, Vaarala O, Suvisaari JM, Gissler M, Grainger M, Linna MS, & Suokas JT (2014). The increased risk for autoimmune diseases in patients with eating disorders. PloS one, 9 (8) PMID: 25147950