Autism spectrum disorder rates in New Jersey 4-year-olds rose by 43 percent over a four-year period, according to a report released Thursday by the federal Centers for Disease Control and Prevention.

This means that one in 35 — 3 percent — of the children in this group have autism spectrum disorder.

The study, which includes data from six other states, found the overall rate of autism for 4-year-olds has increased substantially in the seven states — a nearly 30 percent increase, or one in 59 children.

The findings bolster last year’s CDC study of autism prevalence among 8-year-olds in 11 states. This report found that New Jersey has the highest rate of autism among all the states studied and that the rate of autism nationally appears to be continuing to rise.

“It’s very likely that the next time we survey autism among children, the rate will be even higher,” said Walter Zahorodny, an associate professor of pediatrics at Rutgers New Jersey Medical School, who directed the New Jersey portion of both studies.

The increases appear to reflect actual growth in the rate of children with autism, not just more diagnoses, according to Zahorodny. Education and medical records were used to conduct the study.

But there was no national change in the proportion of children first evaluated by age 36 months, a finding he found troubling. The American Academy of Pediatrics has recommended that all children be evaluated between 18 and 24 months of age for autism, a development disability that leads to difficulties in social interactions and communication.

In fact, New Jersey’s median early evaluation age worsened — from 26 months of age in 2010 to 34 months in 2014.

“Despite our greater awareness, we are not effective in early detection,” said Zahorodny. “Our goal should be systematic universal screening that pediatricians and other health providers provide at regular visits starting at 18 months to identify autism as soon as possible.”

Zahorodny said the rise in the median evaluation age may be a signal that New Jersey needs to increase its capacity to do timely evaluations of all the children who need those services.

Why New Jersey leads the nation in autism prevalence is still open to question and interpretation. Zahorodny said the state’s education system, which is seen as one of the nation’s best overall, availability of preschool services, and better record-keeping may all play roles. However, he added that research using birth records data has not supported the notion that a large proportion of the children in New Jersey with autism have come from other states to access services.

Early detection is viewed as one of the best ways to get children on the autism spectrum the help they need to achieve their full potential. These findings indicate that nationally, many children of color lag behind their white and more affluent peers in terms of first evaluation and age of diagnosis, the associate professor said.

Neither the new study of 4-year-olds nor last year’s report on 8-year-olds include data on Pennsylvania children, and the CDC does not do similar studies that look at all the states. However, the studies’ findings are widely considered to reflect national trends.

Last year’s study among 8-year-olds found a national prevalence rate of one in 59 children, with a rate of one in 34 in New Jersey. The CDC’s Early Autism and Developmental Disabilities Monitoring Network has been studying prevalence rates in 8-year-olds since 2000.

The network’s studies of 4-year-olds began in 2010. The surveys of the younger children help track trends in early detection and are more likely to include children with more severe symptoms or other conditions such as intellectual disability, according to the CDC.