November 7, 2008

Study: Levels of Precipitation May Increase Rate of Autism

Print More

Before deciding where to move after graduation, it might be a good idea to take a look at a new scientific study that suggests that there could be a correlation between higher levels of precipitation and increased incidences of autism in children.
The study, published in The American Medical Association Journal Archives of Pediatrics & Adolescent Medicine, hypothesizes that there is an environmental factor that influences the development of autism in genetically vulnerable children. The lead author of the study was Michael Waldman, the Charles H. Dyson Professor of Management and professor of economics at the Johnson School of Management.
“We were looking at a map of autism rates across the United States and we saw that the rates varied significantly from state to state and that there was a pattern; northern states such as Oregon, Maine, Minnesota and Wisconsin had high autism rates, whereas the southern states, Arizona, Alabama and Tennessee had low autism rates,” Waldman said.
This realization inspired Waldman and his team to conduct statistical tests focused in three states, California, Oregon and Washington, because these states collect information on autism by county, and have significant precipitation variability among counties. For example, Oregon and Washington counties west of the Cascade Mountains receive, on average, almost four times more precipitation than counties east of the Cascades. With this data it was possible for the team to calculate county wide, age specific incidences of autism.
The study hypothesized that if there was a correlation between higher levels of precipitation and more frequent incidences of autism, then the prevalence of autism should be highest in counties that receive higher levels of precipitation, especially in children younger than 3 who were exposed to these levels of precipitation. The results of their research strongly suggested the accuracy of their hypothesis.
Once it was decided that their results were statistically significant, Waldman and his team were able to calculate how much lower autism prevalence rates would be if the genetically predisposed children were removed from areas of high precipitation. The autism prevalence rate would be an estimated 33 percent lower than the mean.
“Historically, most of the medical autism community thought that autism was strictly genetic, but recently with the rise of autism, people still acknowledge that there are children who are predisposed to autism, but that there must also be some type of reaction to the environment. Children could be perfectly healthy for a few years and then become autistic,” said coauthor on the study, Prof. Sean Nicholson, policy and analysis management, who got involved with the project because he was interested in the puzzle that autism presents to the medical community and to society at large.
Waldman and Nicholson, with the help of their associates, have proposed several reasons why elevated precipitation might trigger elevated occurrences of autism in vulnerable children. The majority of these reasons center on the fact that when it precipitates, children spend more time inside. Children may be exposing themselves to an internal toxin, such as household cleaners, or depriving themselves of Vitamin D. Vitamin D deficiency from lack of sun exposure can lead to a deficiency of calcitriol, a neurosteroid associated with brain development.
According to the paper, it is likely that children spending more time inside watch more television, and television viewing by young children has been previously associated with slower cognitive development and problems with language development.
The authors theorize that, if excessive television viewing can produce mild health problems in a typical child, than excessive viewing may cause serious problems, such as autism, in a genetically vulnerable child.
However, the theory that autism can be affected by the environment has been skeptically received by some of the student body.
Nonetheless, Waldman and Nicholson hope that their research will help spur the scientific medical community to conduct more definitive testing in order to develop a solution to prevent more occurrences of autism. “We hope that we have narrowed down the search so that other scientists can focus in on those possible causes,” said Waldman.
Nicholson added, “Our hope is that the medical community will find the results compelling enough that they will want to test these mechanisms.”