Most autistic adults over 40 in the UK remain undiagnosed

89 to 97 per cent of autistic adults aged 40+ years are undiagnosed in the UK, according to the largest review of its kind which was conducted at the Institute of Psychiatry, Psychology & Neuroscience at King's College London. The review indicated that middle-aged and older autistic adults are facing higher rates of mental and physical health conditions than non-autistic adults of the same age, alongside challenges with employment, relationships and wellbeing.

Although research on ageing in autistic populations has increased nearly fourfold since 2012, only 0.4 per cent of research on autism since 1980 has focused on people in midlife or older age. The researchers collated the research to date and conducted a narrative review to understand whether autistic people have different ageing patterns to the general population.

The review, published in the Annual Review of Developmental Psychology, provides a summary of research in this area, highlighting the critical need for more studies to find ways to improve outcomes for this population.

The review was supported by the British Academy and National Institute for Health and Care Research (NIHR) Maudsley Biomedical Research Centre. It highlights substantial challenges for autistic adults in midlife and older age across multiple areas, and identifies barriers to receiving appropriate healthcare support in older adulthood.

Over 89 per cent of autistic adults aged 40+ are undiagnosed

Although people do not 'grow out' of autism, there is a large discrepancy in diagnosis rates between younger and older generations. The authors of the review re-analysed previous research on UK healthcare record data from 2018 and found that 89 per cent of people age 40-59 years and 97 per cent of people age 60+ are estimated to be undiagnosed.

Dr Gavin Stewart, British Academy Postdoctoral Research Fellow at the IoPPN and lead author of the review, said:

"These very high underdiagnosis estimates suggest that many autistic adults will have never been recognised as being autistic, and will have not been offered the right support. This could make them more susceptible to age-related problems, for example being socially isolated and having poorer health.

"The high rates of underdiagnosis also mean that much of our research has systematically overlooked a large proportion of the autistic population, potentially skewing our understanding of how autistic people age, and leaving critical gaps in policy and services."

Higher risk of almost all physical and mental health conditions

The review emphasised a variety of challenges autistic adults in midlife and older age face. The collated evidence shows that middle-aged and older autistic adults have higher rates of almost all physical and mental health conditions compared to non-autistic adults. These include immune diseases, cardiovascular disease, neurological disorders, gastrointestinal disorders, anxiety and depression, as well as conditions associated with older age, such as Parkinson's disease, cognitive disorders, osteoporosis and arthritis.

Particularly concerning findings indicate that older adults with high autistic traits are six times more likely to experience suicidal ideation, thoughts of self-harm, and self-harm. The collated findings also suggest that autistic adults were four-times as likely to have a diagnosis of early-onset dementia compared to non-autistic people. Average life expectancy differed by six years, with autistic people living to age 75 years compared to 81 years for non-autistic people. The authors warn that these figures may be skewed due to high rates of underdiagnoses.

The review noted autistic adults experience barriers to receiving healthcare support, having to navigate systems not designed for them. These barriers included aspects associated with autistic traits, such as communication differences and sensory sensitivities, as well as concerns about continuity of care, uncertainty about which services to access, and limited clinician understanding of autism in adulthood.

In addition to health-related outcomes, poorer outcomes were also seen across employment prior to retirement, relationships and quality of life. There were high rates of social isolation among adults with autism, and the research indicates that strong social support is linked to better quality of life.

Professor Francesca Happé, Professor of Cognitive Neuroscience at the IoPPN and co-author of the review, said:

"Understanding the needs of autistic people as they age is a pressing global public health concern. As autistic people age, the nature of the challenges they face changes. We must adopt a lifespan approach that funds long-term research, integrates tailored healthcare, and expands social supports so that ageing autistic people can live happy and healthy lives."

The review particularly highlighted a lack of longitudinal research which follows autistic people over time to directly measure effects of aging. The researchers emphasise that more research is needed to better understand the experiences of autistic people in midlife and older age, with the aim of improving outcomes for autistic adults as they age.