This paper shows the widely reported stats as less bad (UK):
https://www.thelancet.com/journals/lanepe/article/PIIS2666-7762(23)00195-3/fulltext#:~:text=years) for women.-,The apparent reduction in life expectancy for people diagnosed with,–19.02 years) for women.
https://www.ucl.ac.uk/news/2023/nov/premature-death-autistic-people-uk-investigated-first-time
"The researchers found that autistic men without a learning disability had an average estimated life expectancy of 74.6 years, and autistic women without a learning disability, around 76.8 years.
Meanwhile, the estimated life expectancy for people diagnosed with autism and learning disability was around 71.7 years for men and 69.6 years for women.
These figures compare to the usual life expectancy of around 80 years for men and around 83 years for women living in the UK."
This also :
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6713622/
"Taken together, these studies suggest that individuals with ASD may be at a greater risk for early mortality compared to the general population. However, little is known about the factors that explain this risk."
And this:
https://www.sciencedirect.com/science/article/pii/S1750946722001647
"However, we found only a three-year difference in median age at death between autistic and non-autistic decedents, which is a much smaller disparity than reported in some other studies. This potentially suggests that when autistic people live to the age of 65, they may live to a more similar age as non-autistic peers."
This one mentions the findings of research in Sweden:
https://researchbriefings.files.parliament.uk/documents/POST-PN-0612/POST-PN-0612.pdf
https://www.spectrumnews.org/news/large-swedish-study-ties-autism-to-early-death/
"People with autism are more than twice as likely as their peers in the general population to die prematurely1. Previous studies have hinted at premature death among people with autism, but most of them explored mortality risk in small populations and focused on specific causes of death, such as accidental injury or epilepsy. The new study relies on data from more than 27,000 people with autism and 2.7 million controls from the Swedish population. The researchers found that autism increases mortality risk regardless of the underlying cause of death.
he most common cause of death among people with severe autism is epilepsy, which affects roughly 8 percent of people on the spectrum. By contrast, the most likely cause of death among people with mild autism is circulatory diseases.
Suicide is the only cause of death that is more common among individuals with mild autism than those with severe autism. The risk of suicide in individuals with mild autism is about 10 times higher than in the general population. Women with autism are more likely than men on the spectrum to commit suicide."
Nationality seems to play a big factor (access to healthcare?)
Epilepsy, accident (drowning), and suicide seem key factors.
Maybe someone with a good grasp of reading such material or medical or stats training can glean more.