Danish Study Supports Genetics and the Maternal Environment in Autism

Recurrence Risk for Autism Spectrum Disorders Examined for Full, Half Siblings

http://www.ama-assn.org/ama/home.page

Aug. 19, 2013 — A Danish study of siblings suggests the recurrence risks for autism spectrum disorders (ASDs) varied from 4.5 percent to 10.5 percent depending on the birth years, which is higher than the ASD risk of 1.18 percent in the overall Danish population, according to a study published by JAMA Pediatrics, a JAMA Network publication.

ASDs are neurodevelopmental disorders that are characterized by difficulties in social interaction and communication and also include repetitive behavior and narrow interests. Childhood autism (CA) accounts for about 30 percent of all ASD cases and the prevalence of ASDs has increased during the last two decades, according to the study background.

Therese K. Grønborg, M.Sc., of Aarhus University, Denmark, and colleagues conducted a population-based study in Denmark of all children (about 1.5 million) born between 1980 and 2004. They identified a maternal sibling group derived from mothers with at least two children and a paternal sibling group derived from fathers with at least two children.

“To date, this is the first population-based study to examine the recurrence risk for autism spectrum disorders (ASDs), including time trends, and the first study to consider the ASDs recurrence risk for full- and half-siblings,” the authors note in the study.

The study results suggest an almost seven-fold increase in ASDs risk if an older sibling had an ASD diagnosis compared with no ASD diagnoses in older siblings.

In children with the same mother, the adjusted relative recurrence risk of 7.5 in full siblings was significantly higher than the risk of 2.4 in half siblings.

In children with the same father, the adjusted relative recurrence risk was 7.4 in full siblings and significant, but no statistically significant increased risk was observed among paternal half siblings, the results also indicate.

“The difference in the recurrence risk between full and half siblings supports the role of genetics in ASDs, while the significant recurrence risk in maternal half-siblings may support the role of factors associated with pregnancy and the maternal intrauterine environment in ASDs,” the study concludes.

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Further Readings of Interest

Recurrence of Autism Spectrum Disorders in Full- and Half-Siblings and Trends Over Time A Population-Based Cohort Study

http://archpedi.jamanetwork.com/article.aspx?articleid=1728998

Importance   To date, this is the first population-based study to examine the recurrence risk for autism spectrum disorders (ASDs), including time trends, and the first study to consider the ASDs recurrence risk for full- and half-siblings.

Objectives   To estimate the relative recurrence risk for ASDs in a Danish population, including recurrence in full- and half-siblings, and to examine time trends in ASDs relative to the recurrence risk.

Design, Setting, and Participants   Population-based cohort study in Denmark. All children (about 1.5 million) born in Denmark between January 1, 1980, and December 31, 2004, were identified and followed up to December 31, 2010. We identified a maternal sibling subcohort derived from mothers with at least 2 children and a paternal sibling subcohort derived from fathers with at least 2 children.

Exposures   Children having an older sibling with ASDs are compared with children not having an older sibling with ASDs.

Main Outcomes and Measures   The adjusted hazard ratio for ASDs among children having an older sibling with ASDs compared with children not having an older sibling with ASDs.

Results   The overall relative recurrence risk for ASDs was 6.9 (95% CI, 6.1-7.8), and it did not change significantly over time; similar risks were observed in maternal and paternal full-siblings. The relative recurrence risks were 2.4 (95% CI, 1.4-4.1) for maternal halfsiblings and 1.5 (95% CI, 0.7-3.4) for paternal half-siblings.

Conclusions and Relevance   Our population-based recurrence risk estimate is lower than the recently reported estimates from clinical samples. Our results demonstrate no time trend in the ASDs recurrence risk as seen in the ASDs prevalence. The difference in the recurrence risk between full- and half-siblings supports the role of genetics in ASDs, while the significant recurrence risk in maternal half-siblings may support the role of factors associated with pregnancy and the maternal intrauterine environment in ASDs.

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Further Commentary

1 Autistic Child in Family Hikes Risk for More

www.medpagetoday.com/Pediatrics/Autism/41061

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This entry was posted in Autism, Environment, Genetics, Physiology. Bookmark the permalink.

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