One in 127 people has autism, global prevalence study finds

An estimated 61.8 million people worldwide were on the autism spectrum in 2021, according to a study that highlighted the need for early detection and support of the developmental condition.

Autism affects about one in 127 people, researchers from the 2021 Global Burden of Disease Study found.

That is a jump from the one in 271 reported in 2019, which may have underestimated the condition – characterised by ongoing challenges in social communication, interaction, sensory processing, and repetitive behaviours or interests, and, in some cases, intellectual disability, with varying levels of severity.

Autistic people face a heightened risk of social isolation, academic or workplace challenges, and may require psychosocial support well into adulthood, the researchers said, as they ranked autism among the top 10 non-fatal health challenges for young people.

They touted the likelihood of vast improvement in outcomes when the condition was detected early and lifelong support provided.

“The persistence of the health burden across the lifespan demonstrates the need for policy planning and health-care provision that caters to autistic individuals at all stages of life,” they wrote in the study, published on Dec 19 in the journal The Lancet Psychiatry.

The analysis, based on data from 34 countries, found autism was significantly more common in boys and men, with a global age-standardised sex ratio of 2.1 to one.

Gender bias

Previous studies estimated a ratio of more than four to one, likely reflecting a bias that meant females with autism were often overlooked and therefore missed out on receiving support, said Dr Damian Santomauro, the report’s lead author and head of the epidemiology and burden of disease research stream at the University of Queensland and Park Centre for Mental Health.

Prevalence varied widely by region, ranging from one in 163 people in tropical Latin America to one in 65 in high-income Asia-Pacific countries, the study found.

Japan had the highest prevalence at 1,587 per 100,000 people, compared with 588 in Bangladesh and 614 in Brazil.

Several factors contribute to these geographical differences, including varying exposure to risk factors, cultural differences in behavioural norms, the validity and selection of screening and diagnostic tools, participants’ responses to surveys, and even their willingness to participate, Dr Santomauro and colleagues said.

Professor of autism Andrew Whitehouse from The Kids Research Institute Australia in Perth said: “This is an important study because it very clearly shows the impact that autism has on the individual, the family and the broader community.”

He added: “The paper should redouble global efforts to find and implement ways to identify autism early, so that we can maximise the life opportunities for autistic people.”

Is autism increasing?

The new research found that, contrary to some studies suggesting a rise in the incidence of autism, the prevalence of autistic traits in the population has remained relatively stable over time.

“Everyone’s been asking, is the prevalence of autism increasing?” Dr Santomauro said in an interview, noting that some data from disease registries have shown “astronomic” growth. “But we’ve wondered, is this because awareness is increasing and more people are getting diagnosed?”

Studies using random sampling and population screening have not shown a significant change, he added.

While early detection and intervention are widely recognised as essential, Dr Santomauro and his colleagues emphasised the importance of addressing not only the needs of autistic children and teenagers but also those of adults, who are often under-represented in research and services.

Assessment delays

Researchers highlighted the issue of long wait times for assessments, noting that delays of six to 24 months are not uncommon, depending on the setting, region, and age of the individual.

In infants with more severe developmental delays, signs of autism can appear as early as 12-24 months, while those with strong cognitive skills and subtler presentations may not exhibit autism-related concerns until elementary school or even their teenage years, said Dr Susanne Duvall, an associate professor of paediatrics and psychiatry at Oregon Health & Science University.

“As social and school demands become increasingly complex and nuanced, the demand on verbal and non-verbal communication skills, independence, multitasking and organization increases,” Dr Duvall said in an e-mail. “Children may struggle to keep pace with peers, which can lead to gaps over time.”

She added that while many centres prioritise assessments for younger children because early treatment is typically most effective, this focus can result in significant delays in diagnosis and support for older children with autism concerns.

Girls, in particular, are more likely to experience delays in diagnosis due to fewer outward behavioural symptoms and difficulties. BLOOMBERG