Children of obese fathers had an increased risk for developing autistic disorder and Asperger disorder, and the risk grew with increasing body mass index (BMI), wrote Pål Surén, MD, MPH, of the Norwegian Institute of Public Health in Oslo, and colleagues, in the May issue of Pediatrics.
The risk of autistic disorder was 0.27% in children with obese fathers (BMI ≥30 kg/m2), compared with 0.14% in children whose fathers were not overweight or obese (BMI <25 kg/m2), for an adjusted odds ratio of 1.73 (95% CI 1.07-2.82).
Compared with a normal-weight father, being born to an obese father doubled the risk for Asperger disorder (aOR 2.01, 95% CI 1.13-3.57) for children ages 7 and up, although the absolute risk for this disorder was quite small — 0.38% in children with obese fathers and 0.18% in children with normal-weight fathers.
However, the researchers failed to find a significant link between maternal obesity and child autism even though obesity was equally prevalent in mothers (9.6%) and fathers (10%) in the study population.
These results differ from a 2012 study that found that mothers who were obese before pregnancy had a 67% increase in having children with autism spectrum disorders.
“We had thought that maternal obesity may somehow be related to autism, but this is the first time anyone has looked at paternal weight, and the findings suggest we may have gotten it wrong,” commented Andrew Adesman, MD, chief of developmental and behavioral pediatrics at Steven & Alexandra Cohen Children’s Medical Center of New York in Lake Success, N.Y.
Adesman, who was not involved in the current research, pointed out that it’s not clear from either of the studies if obesity plays a causal role in autism. Even if future studies did demonstrate causality, the impact of parental obesity on autism spectrum disorders is likely to be small, he added.
“Most of the children with autism in this study were not born to obese fathers and most of the children born to obese fathers did not develop autism,” he told MedPage Today. “The risk (for autistic disorder) increased from 15 per 10,000 cases (children with normal-weight dads) to 25 in 10,000 cases (children with obese dads), which is still very, very low.”
The analysis included a sample of close to 93,000 children (mean age 7.4) in Norway derived from the Norwegian Mother and Child Cohort Study.
At the end of follow-up in December 2012, autism spectrum disorders had been diagnosed in 419 (0.45%) of the children, specifically 162 (0.17%) cases of autistic disorder, 103 (0.11%) of Asperger disorder, and 154 (0.17%) of pervasive developmental disorders-not otherwise specified (PDD-NOS).
Among those cases, 43% had been clinically assessed through the Autism Birth Cohort Studywhile 57% had autism spectrum disorder diagnoses confirmed by a specialist.
In mothers and fathers, obesity was associated with a lower education level and higher levels of smoking.
Neither maternal nor paternal BMI was associated with the risk of PDD-NOS in children, and the associations between maternal obesity and autistic disorder and Asperger disorder were similar. The risk was increased for both disorders, but this increase was substantially attenuated by adjustment for paternal BMI, the researchers wrote.
The study’s primary limitation was self-reported height and weight measures for the parents, which were not validated through objective measurements.
“The potential effects should be further investigated through attempts at replication of our analysis, and, if these are positive, through genetic and epigenetic studies,” the researchers concluded. “It should also be explored whether paternal overweight and obesity are associated with an increased risk of other neurodevelopmental disorders in children.”
The study was funded by the Research Council of Norway and the NIH.
The authors reported no relevant relationships with industry.
The Norwegian Mother and Child Cohort Study was funded by the Norwegian Ministry of Health and Care Services, the Norwegian Ministry of Education and Research, the Research Council of Norway/FUGE, the National Institute of Neurologic Disorders and Stroke (NINDS), and the National Institute of Environmental Health Sciences. The Autism Birth Cohort Study was funded by NINDS.