The first-ever national estimate of the prevalence of autism in the United States finds the behavioral disorder affects up to one in every 175 school-age children — a total of more than 300,000 youngsters. That finding comes from researchers at the U.S. Centers for Disease Control and Prevention in Atlanta, who presented their conclusions at a press conference on Thursday. The agency’s estimates are based on interviews conducted in 2003 and 2004 with the parents of nearly 98,000 children aged 4 to 17. In two national surveys — the National Health Interview Survey (NHIS) and the National Survey of Children’s Health (NCHS) — parents were asked: ‘Has a doctor or health-care provider ever told you that [your child] has autism?’ ‘Estimates of diagnosed autism from these surveys were 5.7 per 1,000 school-age children from the NHIS, and 5.5 per 1,000 school-age children from the NSCH,’ said Laura Schieve, an epidemiologist with the CDC’s National Center on Birth Defects and Developmental Disabilities (NCBDDD). Those ratios correspond to about one in every 181 children and one in every 175 children, respectively, the researchers said. ‘Together, these two national surveys of parents suggest that over 300,000 school-age children […]