Autism has received increasing amounts of attention in recent years. The increases in autism rates in the US have spurred other countries to reassess their rates of autism.
A recent study found that the UK's rates of autism in children were still well below the rates found in the US.
The US, the UK and Denmark all saw considerably large increases in the number of autism diagnoses during the 1990s.
The reasons for the increase have continued to be debated in the medical community.
It is uncertain why the UK rates differ so much from the US rates.
This study, led by Brent Taylor, of the Institute of Child Health in London, United Kingdom, looked at how rates of autism diagnosis have changed in the UK over the past few decades.
The data for the study came from the UK General Practice Research Database and was intended to be compared to the data released last year by the US Centers for Disease Control and Prevention (CDC).
The researchers first determined the percentage of 8-year-olds in the UK who had autism spectrum disorders.
Then they calculated how many new children had been diagnosed each year with autism when the children were between the ages of 2 and 8.
The number of 8-year-olds who had autism in the UK had not changed much from the 1990s up through 2004 to 2010.
That number was approximately four autistic boys out of every 1,000 boys and one autistic girl out of every 1,000 girls.
These numbers contrast with the US CDC numbers in 2012 that found one in 88 children aged 8 had autism.
The researchers also did not find any big changes in how frequently autism was diagnosed in the UK among children.
Throughout the years 2004 to 2010, about 1.2 boys per 1,000 boys (or 12 per 10,000) and 0.2 girls per 1,000 girls (or 2 per 10,000) were diagnosed with autism in the UK.
"Following a fivefold increase in the annual incidence rates of autism during the 1990s in the UK, the incidence and prevalence rates in 8-year-old children reached a plateau in the early 2000s and remained steady through 2010," the researchers wrote.
"Whether prevalence rates have increased from the early 2000s in the USA remains uncertain," they wrote.
Glen Elliott, MD, PhD, a clinical professor at the Stanford University Department of Psychiatry and Behavioral Sciences, said the authors have done an impressive job of evaluating the changes in autism rates in the UK.
"Especially valuable for those of us in the United States is their effort to compare and contrast trends between the two countries," he said. "They note that both countries experienced the still-unexplained, major increase in prevalence rates in the 1990s, whereas, in the UK, during this period, rates held steady."
Meanwhile, he noted US reports of autism continued to increase.
"Understanding the different research methods used in the two countries and clarifying why rates have diverged so dramatically in the past decade should yield invaluable insights into possible [causes] of the phenomenon," Dr. Elliott said.
"At the same time, their results help to resolve one controversy, which is whether the apparent increase in autism rates was an artifact of improved detection: the steadiness of prevalence rates of the period study do not support that explanation," he said.
This study was published October 16 in the journal BMJ Open. The research did not use outside funding, and the authors reported no conflicts of interest.