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The CDC released new data on autism which found an increase in New Jersey. Getty Images

The percentage of 4-year-olds in New Jersey with autism spectrum disorder (ASD) increased 44 percent between 2010 and 2014, according to a new report by the Centers for Disease Control and Prevention (CDC).

This goes against previous CDC data that suggested the rates were leveling off.

“It is now clear that what we saw in 2016 was just a pause along the way. It remains to be seen at what point ASD rates will plateau,” said Dr. Walter Zahorodny, PhD, an associate professor of pediatrics at Rutgers New Jersey Medical School who directed the New Jersey portion of the study, in a press release.

In 2014, 2.8 percent of New Jersey children aged 4 years old were identified as having ASD. This is an increase over the previous two reports — in 2010 and 2012.

Only two other sites — Arizona and Missouri — had consistent data for all three years. The rates of ASD at those sites remained steady during this time.

Dr. Diana Robins, PhD, interim director and professor at the A.J. Drexel Autism Institute, said the “steady increase” seen in New Jersey for 4-year-olds is similar to that seen for 8-year-olds in other CDC data.

However, “More concerning than the increase in New Jersey numbers per se are the fairly striking differences across sites measuring 4-year-old prevalence,” said Robins, “above and beyond what can be explained by the types of records available.”

In 2014, the ASD rates ranged from less than 1 percent in Missouri to a high of 2.8 percent in New Jersey. The average was 1.7 percent.

Overall ASD rates in the United States among 8-year-olds increased from 6.7 percent in 2000 to 16.8 percent in 2014, according to the CDC.

Researchers can’t explain why ASD rates are on the rise overall or in New Jersey, but there are several possible explanations.

For the new study, differences in data available in each state could have led to New Jersey overestimating its ASD rates, while other sites underestimated theirs.

“Before we can evaluate how concerning the high prevalence of ASD is in New Jersey,” she said, “it will be important to sort out some of these other factors that affect measurement.”

Greater awareness and improved detection of ASD in recent years could have also led to more children being diagnosed. Robins said this may account for “much” of the increase, but not all.

Scientists are also looking at environmental factors that increase the risk of ASD, such as children being born prematurely, being born to parents older than age 30, or maternal illness during pregnancy.

These are unlikely to cause ASD by themselves, but instead combine with genetic factors to increase a child’s risk.

“It will be quite some time before people can identify whether New Jersey has higher levels of any specific risk factors compared to other sites in the CDC’s surveillance network,” said Robins.

The new study is based on information from the Early Autism and Developmental Disabilities Monitoring Network. Seven sites across the United States are included in the report.

Other states in the study were Arizona, Colorado, Missouri, North Carolina, Utah, and Wisconsin.

Researchers screened the health records of nearly 71,000 children aged 4 years old in 2014. Three states also looked at education records.

Based on this, they identified more than 1,200 children with autism. In New Jersey, 514 of 18,112 children were identified with autism.

Researchers found other differences in ASD rates — including for gender and race and ethnicity.

ASD rates were higher for boys than girls for all states and in all years. Robins said several factors could be behind this.

For example, criteria for diagnosing ASD are primarily based on symptoms in males, so they may not detect ASD as well in females. Females may also be better at masking symptoms of ASD. Or there could be other factors that protect girls from developing ASD.

In some states, the differences in ASD rates between white people and minorities decreased from 2010 to 2014.

“This is a good thing,” said Robins, “if it means that children who are minorities are being detected at similar rates compared to their white peers.”

Perhaps more concerning is that the age at which children are first diagnosed with ASD hasn’t decreased in recent years.

“Children who are evaluated for autism early — around their second birthday — often respond better to treatment than those who are diagnosed later,” said Zahorodny.

In the new study, the average age of a child’s first ASD diagnosis ranged from 28 months in North Carolina to 39 months in Missouri and Wisconsin.

Delays in identifying children who are at risk means losing the chance to help them early on.

”We know experts can diagnose ASD very early for many children, and that it is important to start treatment young to maximize the benefits of early intervention,” said Robins. “Now we need to do a better job making these services available to children in the community.”