Washington D.C, Aug 6 : Turns out, genetics can place you at risk as according to a recent study, the chances of a kid developing an autism spectrum disorder (ASD) is 14 times higher if his or her older sibling has ASD.
The Kaiser Permanente study also found the risk level was consistent across gestational age at birth. Autism is a neurodevelopmental disorder defined by impairments in social interaction and communication, as well as restricted and repetitive patterns of behavior.
It occurs in 1 in 68 children, according to the most recent data from the Centers for Disease Control and Prevention.
The cause of autism is unknown, but research has identified a number of different genetic and environmental factors that may play a role in its development.
"Our study provides additional insights into how autism affects siblings," explained senior author Darios Getahun.
"These findings also contribute to a better understanding of the influence of factors such as gender on autism risk." The researchers focused on at least two siblings born to the same mother between 28 and 42 weeks of gestation from 2001 through 2010.
Researchers examined the medical records of the 53,336 children born during this time, of which 592 were diagnosed with ASD, and found that children with older siblings who had ASD had an ASD rate of 11.3 percent compared to 0.92 percent for those with unaffected older siblings.
Compared with gestational age-matched younger siblings without ASD diagnosis, those born at term (37-42 gestational weeks), who had an older sibling diagnosed with ASD, had more than 15 times the increased risk for ASD diagnosis.
Younger siblings, who were born at preterm (28-36 gestational weeks) and had an older sibling diagnosed with ASD, had an almost 10 times increased risk for ASD.
Younger boys with ASD, who had older brothers, were much more likely to be affected by the disorder than younger girls with older sisters (15 percent vs 7 percent, respectively).
"It's possible that parents who have an older child with an autism diagnosis are more likely to have their younger siblings tested, too, resulting in a higher rate of diagnoses among younger siblings, compared with parents who do not have children diagnosed with an autism spectrum disorder," noted Getahun.
The researchers also noted that the gender difference observed in this study could be due to biases in diagnosis and reporting.
The study is published in Journal of Developmental and Behavioral Pediatrics..