90% of people with autism over the age of 40 remain undiagnosed

90% of people with autism remain undiagnosed                                      

Autism eludes doctors: 9 out of 10 patients remain undiagnosed

Autism diagnoses have increased sharply in recent decades, leading to speculation that the condition is new or caused by recent environmental factors. However, a comprehensive review of research on adults with autism over the age of 40 paints a very different picture, showing that autism extends into older generations, with up to 90% of cases remaining undiagnosed.

Researchers from King's College London revealed a startling figure in a new study that focused on what is known about autism in middle and older adults. They found that the vast majority of people with autism over the age of 40 remain undiagnosed, with serious consequences for health, well-being, and quality of life.

Risk of Early-Onset Dementia

Studies have shown that individuals with autism are four times more likely to develop early-onset dementia, six times more likely to experience suicidal thoughts, and have a life expectancy six years lower than their non-autistic peers. In the study, analysis of UK health records revealed that approximately 89% of adults with autism aged 40 to 59—and 97% of those over 60—do not have a formal diagnosis. In fact, nine out of 10 older adults with autism may be living with the condition without any recognition or support.

Social Isolation and Poor Health

Dr. Gavin Stewart, lead researcher of the study from King's College London, said: "These very high estimates of underdiagnosis suggest that many adults with autism have never been diagnosed with autism and will not receive appropriate support." He explained that "this could make them more vulnerable to age-related problems, such as social isolation and poor health."

In addition to mental health challenges, older adults with autism experience higher rates of a range of serious conditions, including immune, cardiovascular, and gastrointestinal disorders, as well as age-related problems such as Parkinson's disease, osteoporosis, and arthritis.

While the study focuses on the UK, a similar pattern exists worldwide. According to the US Centers for Disease Control and Prevention, 1 in 150 children born in 1994 had a diagnosis when data was evaluated in 2000. Currently, approximately 1 in 31 children born two decades later, in 2014, received an autism diagnosis (data were evaluated in 2020).

A growing and medically complex population

According to the results of a 2024 study conducted in the US, rates of autism spectrum disorder (ASD) diagnoses rose significantly between 2011 and 2022, particularly among young adults, females, adults, and children from certain racial or ethnic minority groups. The researchers added that "diagnostic prevalence trends, derived from health system data, could contribute to allocating resources to meet the needs of this growing and medically complex population."

Despite increasing awareness and diagnoses around the world, older adults remain underreported in statistics. One major reason lies in how autism has been historically defined. For most of the 20th century, autism spectrum disorder (ASD) was narrowly described as "infantile autism," a now-obsolete term often associated with intellectual disability. 

Like attention-deficit/hyperactivity disorder (ADHD), the psychiatric focus was on males. Diagnostic criteria for ASD have gradually expanded since the 1980s, providing a more accurate picture of those on the autism spectrum. This means that today's high prevalence is largely explained by changes in recognition, standards, and awareness.

Problems with Work and Relationships

In the latest study, researchers found that, in addition to poorer health outcomes compared to the general population, older adults faced challenges accessing healthcare and support, as diagnosis and treatment were still skewed toward children. They also had a higher rate of problems related to work and relationships later in life. “Understanding the needs of people with autism as they age is a pressing global public health concern,” said Francesca Happé, study co-author and professor of cognitive neuroscience at King’s College London.

“As people with autism age, the nature of the challenges they face changes. A life-course approach that funds long-term research, integrates tailored healthcare, and expands social support is essential so that older people with autism can live happy and healthy lives,” Happé added.