Sunday, 16 March 2014

Obesity and autism (again)

The paper by Phillips and colleagues [1] looking at the prevalence of 'unhealthy weight' in relation to developmentally-defined conditions including autism brought me to writing this update post on the topic of obesity and autism. As you might glean from that previous sentence, obesity and over-weightness(?) has been talked about before on this blog (see here and see here for example). My recent discussion in relation to findings of elevated plasma leptin in cases of autism (see here) adds to the interest in this topic, as does a post on the issue of sedentary behaviours and autism (see here).

I wanna dance... @ Wikipedia 
The Phillips data, based on the body mass index (BMI) calculation suggested a few important trends might need further action based on the primary issue that: "Obesity was elevated among adolescents with all DD [developmental disabilities] types, and was highest among the autism subgroup". Further: "Adolescents with either a DD or obesity had higher prevalences of common respiratory, gastrointestinal, dermatological and neurological conditions/symptoms than nonobese adolescents without DDs". This last point was, in particular, of interest to me because it kinda hinted that issues such as gastrointestinal (GI) problems noted on more than one occasion in relation to autism, may very well tie into overall physical health. By saying that however, I'm not insinuating that all GI problems are 'caused' by obesity when it comes to autism, because as I've talked about before, autism is a very heterogeneous condition in terms of presentation and comorbidity. Oh and perhaps I should introduce the possibility that BMI and autoimmune conditions might be linked at this point too given the 'overlap' between these concepts with autism.

Outside of discussions about the usefulness of the BMI measure, whether 'fat and fit' is a possibility or the growing interest in the notion of the TOFI (which may yet be important to some of those leptin-autism findings), the Phillips paper led to me to have a closer look at some of the research literature in this area over the past couple of years. So, in no particular order, here goes:

The study by Zuckerman and colleagues [2] looked at the frequency of overweight and obesity in a sample of 376 children diagnosed with an autism spectrum condition. They reported that approximately 18% of their cohort were categorised as being overweight and 17% were obese. When it came to looking at other health-related measures and variables for those children falling into one or both of those weight-related categories, one of the primary correlates was that of sleeping difficulties and onwards the use of something like melatonin (the molecular handy-person).

Then we have the study by Egan and colleagues [3] which followed a similar formula in relation to looking at the rates of overweight and obesity in their cohort of 273 children with autism. For them: 17% of their sample were categorised as overweight and nearly 22% had "a BMI percentile in the obese range". Just in case you want a visual representation of what ratio of height to weight corresponds to the obese range, have a look at the graphic at the end of the report shown here. I should also mention that the Egan data also suggested differences in the proportions of overweight and obesity according to differing diagnoses along the autism spectrum which potentially introduces some influence from factors such as cognitive or language ability into the equation. Indeed, even whether certain parts of the autisms might be prone to weight issues? Gut bacteria perhaps... nah.

On the topic of cognitive functions, the paper by de Winter and colleagues [4] more generally looked at the frequency of overweight and obesity in a sample of adults diagnosed with a range of intellectual disabilities including autism. Interestingly their measures were not just confined to BMI but also included "waist-to-hip ratio (WHR) and skin fold thickness". Waist-to-hip ratio has been suggested to be a better marker of health risk than BMI for some conditions (see here). The de Winter results: "Women, people with Down syndrome, higher age, less severe ID, autism, people who are able to eat independently, preparing meals and doing groceries independently, people with physical inactivity and use of atypical antipsychotics were significantly more at risk of being overweight or obese". Quite a few variables there, and certainly quite a few potential avenues of intervention too.

And finally we have the paper by Tyler and colleagues [5]. Again the focus was on adults, and specifically adults with autism (N=108). Based on looking at electronic patient records, various factors were included for analysis and their findings.. "rates of chronic disease included 34.9% for obesity, 31.5% for hyperlipidemia, and 19.4% for hypertension". The figures for obesity are certainly a lot higher than for the other studies but bear in mind this was an investigation based on adults.

What I think we can take from this collected data are a few details. First, and probably most obviously, autism as a diagnosis is not protective against being overweight or even obese. Yes, one has to be careful to bear in mind the important side-effects which various medicines can have on issues like weight gain (depending also on how long they are used for). But I'm pretty sure that not every person with autism falling into those overweight and obese categories for these studies were taking those kinds of medicines, and indeed, even something like melatonin (with some history with regards to autism) might even mitigate some weight effects.

Second, there is some indication that overweight and obesity may be over-represented when a diagnosis of autism is present. I have to say that I'm not totally sold on the idea that there is a vast difference between the frequencies reported in autism and those present in the general population as a whole but I'm willing to concede that autism might place someone towards the top end of any risk of weight issues. Whether this trend changes in line with what seems to be emerging from the examination of US population pediatric obesity rates [6] is fodder for speculation.

Finally, knowing what is out there in the peer-reviewed research literature and how overweight and obesity might place someone at elevated risk of other health complaints and even early mortality, the question must be: what can we do about it? This is perhaps a trickier question that you might first think. Parents, caregivers and professionals can implement strategies to minimise the risk of such issues in childhood (accepting that the relationship between weight and exercise is not necessarily as straight-forward as just do more and lose weight) but for adults... well, adults tend to have a lot more say on how their lives are run than children (see this discussion on Gillick competency). What this means is that even when presented with someone who may have profound difficulties in relation to autism and/or learning disability, one cannot just start making dietary changes or introducing exercise regimes without attempting to infer what they want to do with their lives. Indeed, as per what goes on in the population as a whole, not everyone enjoys doing exercise and not everyone really wants to think about how food choices can influence weight and subsequent health issues. So one needs to tread or even walk carefully.

And just as I post this entry, so I can also direct you to the peer-reviewed open-access mega review on all things autism and obesity from Curtin and colleagues [7]...

----------

[1] Phillips KL. et al. Prevalence and Impact of Unhealthy Weight in a National Sample of US Adolescents with Autism and Other Learning and Behavioral Disabilities. Matern Child Health J. 2014 Feb 20.

[2] Zuckerman KE. et al. Overweight and Obesity: Prevalence and Correlates in a Large Clinical Sample of Children with Autism Spectrum Disorder. J Autism Dev Disord. 2014 Feb 2.

[3] Egan AM. et al. Obesity in young children with autism spectrum disorders: prevalence and associated factors. Child Obes. 2013 Apr;9(2):125-31.

[4] de Winter CF. et al. Overweight and obesity in older people with intellectual disability. Res Dev Disabil. 2012 Mar-Apr;33(2):398-405.

[5] Tyler CV. et al. Chronic disease risks in young adults with autism spectrum disorder: forewarned is forearmed. Am J Intellect Dev Disabil. 2011 Sep;116(5):371-80.

[6] Ogden CL. et al. Prevalence of Childhood and Adult Obesity in the United States, 2011-2012. JAMA 2014; 311: 806-814.

[7] Curtin C. et al. Obesity in children with autism spectrum disorder. Harv Rev Psychiatry. 2014 Mar-Apr;22(2):93-103.

----------

ResearchBlogging.orgPhillips KL, Schieve LA, Visser S, Boulet S, Sharma AJ, Kogan MD, Boyle CA, & Yeargin-Allsopp M. (2014). Prevalence and Impact of Unhealthy Weight in a National Sample of US Adolescents with Autism and Other Learning and Behavioral Disabilities Matern Child Health J DOI: 10.1007/s10995-014-1442-y