It is not clear exactly what the prevalence of autism is amongst the population of adults with learning disabilities. Estimates vary amongst published studies and a recent review carried out by the team at Improving Health and Lives  looked at a range of studies that attempted to estimate the prevalence of autism among community-based or total population samples of adults with learning disabilities.

Although exact prevalence may be difficult to pin down, published studies have consistently shown higher rates than found in general adult population and the IHAL review used two estimates – the first of 20% (close to the median rate across studies) and an second 30% (which was the higher rate reported by studies)

NICE Guidance

Existing NICE guidance for autism in adults identifies a range of psycho-social interventions. Whilst not replacing the existing guidance, NICE run a programme of Evidence Updates, and last month saw the publication of a new Evidence Update on Autism in Adults.

The Evidence updates are managed by an expert advisory group who carried out a systematic search from 9 September 2011 to 27 November 2013.

After removing duplications and other sifting, they critically appraised 10 items. The group then identified any changes in the evidence base. Any decisions about changes to existing guidance will be informed by the evidence update process.

Autism in ageing population

In relation to adults with learning disabilities, there were one or two new pieces of evidence that the group draw attention to, for example in relation to autism and intellectual disability in an ageing population which found that medication for behavioural problems was more widely used among adults with autism and that there was a greater need for support to manage behavioural problems among those with autism and intellectual disability as against those with intellectual disability alone. The authors of the evidence update conclude that this may suggest a need for higher levels of support for behavioural problems in adults with autism and intellectual disability than in those with intellectual disability alone.

Epilepsy and mortality

They also looked at two studies relating to epilepsy and mortality in adults with autism which, despite limitations in methodologies suggested an increased mortality risk for adults with autism, which may be related to the presence of intellectual disability and co-morbid medical conditions (particularly epilepsy).

Diagnosis and assessment

In relation to the diagnosis of autism in adults with intellectual disabilities, they looked at one study which considered the usefulness of two diagnostic tools, currently recommended by NICE for diagnosis and assessment, the Autism Diagnostic Interview – Revised (ADI-R) and the Autism Diagnostic Observation Schedule – Generic (ADOS-G). The study suggested that if the ADOS was used alone, it may result in over-diagnosis of autism, but that using the ADI-R identified the key role played by developmental history in diagnosis of autism in adults.

Links

Autism in adults Evidence Update May 2014 A summary of selected new evidence relevant to NICE clinical guideline 142 ‘Autism: recognition, referral, diagnosis and management of adults on the autism spectrum’ (2012) Evidence Update 59

Autism: recognition, referral, diagnosis and management of adults on the autism spectrum, Issued: June 2012 NICE clinical guideline 142,

The Estimated Prevalence of Autism among Adults with Learning Disabilities in England, Emerson E & Baines S, Improving Health and Lives