Another 2015 study examined students in U.S. special education programs between 2000 and 2010. The number of autistic children who enrolled in special education tripled from 93,624 to 419,647. In the same time frame, however, the number of children labeled as having an “intellectual disability” declined from 637,270 to 457,478. The shift of children from one diagnostic category to another explained two thirds of the increase in autism in this population, researchers say.<p><a href="https://www.scientificamerican.com/article/the-real-reason-autism-rates-are-rising/" rel="nofollow">https://www.scientificamerican.com/article/the-real-reason-a...</a><p>Some portion of the rise in autism rates may be unrelated to better diagnosis. The likelihood of having an autistic child increases for older parents, and there is a societal trend toward delaying childbirth across developed countries. Children who are born prematurely are also at a heightened risk of autism, and improved neonatal care means many more of these children are surviving to childhood and beyond.