IS THE OBESITY EPIDEMIC BEHIND THE RISE IN AUTISM? A Glasses on the Head Moment…

IS THE OBESITY EPIDEMIC BEHIND THE RISE IN AUTISM?

A Glasses on the Head Moment

By Sean Kenniff, MD

www.healthapalooza.com

Sometimes we just don’t notice the obvious, even if we are scientists. This is a tale of two epidemics.

Forty years ago we were a lean and robust nation. But at some point during the 1970s, our bellies and backsides began to steadily balloon, and our weight gain accelerated through the eighties and nineties. Today, two thirds of all American adults are overweight or obese according to CDC statistics. Nowhere is the obesity epidemic causing more concern than in the delivery room. Many normal weight women become overweight or obese during their pregnancies, and roughly 30 percent of women are overweight or obese at the time of conception. Obesity, at any point during pregnancy, places the health of the mother and her unborn baby in serious jeopardy.

If you were born in the 1970s your chances of developing autism were pretty slim—about 4 in 10,000. Today, 1 in every 110 children has an autism spectrum disorder (ASD). This dramatic rise in the number of children with autism is partly due to improved diagnostic methods and more inclusive diagnostic criteria. However, even by conservative estimates, the number of children with autism has significantly increased since the 1980s. Addressing the most recent rise, Dr. Catherine Rice from the CDC suggested the data was perplexing.

“These new numbers are concerning, and indicate that even more individuals, families and communities are struggling to find answers,” Rice said.

But are researchers asking the right questions? These two modern epidemics—obesity and autism—seem to have evolved in parallel and during the same time period. Could obesity be fueling the rise in autism?

If you are starting to put the puzzle pieces together, congratulations. Because it appears scientists have yet to do so.

Somebody Must Have Studied This Already…Right?

Using Medline, the database of scientific studies maintained by the National Library of Medicine, a search for “pregnancy obesity and autism” yields just five results. A search for “maternal obesity and autism” yields twenty-one results. In both searches none of the studies cited directly examines the possibility of a link between prenatal obesity and autism. Not to be sexist, a search for “paternal obesity and autism” proves equally fruitless. By contrast, a search for “pregnancy obesity and hypertension” yields 802 scientific studies—many of which are direct investigations into a link, and a search for “pregnancy obesity and risks” yields 2588 studies.

Why hasn’t the connection between autism and obesity been explored? For one thing, autism is not a single disease, and as such, it probably does not have a single cause. A combination of genetics and environmental factors is thought to play a critical role in increasing the risk of autism. The risk of obesity is also heavily influenced by genetics and the environment, but psychological and emotional factors are thought to be equally significant. With two such unpredictable and multifaceted disorders, it is difficult to pinpoint any correlation, says Dr. Jacob Seligsohn, a primary care pediatrician who also specializes in childhood autism at Joe DiMaggio Children’s Hospital and Pediatric Associates in Hollywood, Florida.  

“Autism is a very complex condition and simply two variables themselves—maternal obesity and autism—are hard to correlate with each other,” Dr. Seligsohn says.

Although the scientific evidence to support a link between obesity and autism is circumstantial, it is compelling. 

Though the World Health Organization does not track global statistics on autism, the available data suggests the world’s most overweight nations—namely the United States, the United Kingdom, and Australia—also have the highest prevalence of autistic disorders. And across the world as the rates of obesity have risen, so have the rates of autism.

It is well known that maternal obesity can have a devastating impact on the baby’s developing nervous system. Obesity during pregnancy raises the risk of hydrocephalus—or “water on the brain”—by 60 percent and it doubles the risk of neural tube defects, like spina bifida and anencephaly.

The rate of diabetes during pregnancy has doubled in recent years, and the obesity epidemic is believed to be chiefly responsible for the increase. Gestational diabetes doubles the risk of autism according to 2009 a meta-analysis published in the British Journal of Psychiatry. It’s possible that the high blood sugar levels or growth factor disturbances seen with diabetes may adversely affect the developing brain.

A November 2009 study published in the Journal of Child Psychology and Psychiatry found maternal obesity was associated with a two-fold increase in Attention Deficit Disorder in children. Interestingly the researchers found maternal obesity only increased the risk of inattentive behaviors in the children, not hyperactive behaviors. Most children with autism have difficulties maintaining attention.

It has also been recently discovered that obesity can impair the immune system, making expectant mothers more prone to infections. Infections during pregnancy—like CMV and rubella—can result in autistic behaviors in children.

Do Autism and Obesity Have a Common Enemy?

The sweetener high fructose corn syrup (HFCS) was rapidly introduced into the U.S. food chain between 1975—1985. While HFCS has long been a suspect in causing, or contributing to the obesity epidemic, the sweetener has never been connected to autism. But two recent studies from the Institute for Agriculture and Trade Policy (IATP) are raising some concerns. In the first study almost half of the commercially available HFCS samples they examined tested positive for mercury. In the second study the researchers found mercury in one-third of 55 popular consumer products that listed HFCS as the first or second ingredient. While neither study identified the form of mercury detected, methylmercury is known to impair neural development in the developing fetus, and exposure to the heavy metal has been implicated as an autism risk in the past. More recent studies however suggest there is no link between autism and mercury.

Obesity recently surpassed smoking cigarettes as the nation’s leading cause of preventable disease. Obesity is known to raise the risk of at least 30 other conditions—including heart disease and several types of cancer. Having excess fat tissue alters metabolism, impairs the immune system, increases levels of inflammation, and often renders important hormones ineffective. Any of these physiological disturbances could pose a theoretical risk to the brain of a developing baby.

“Because so much is unknown about autism, any reasonable hypothesis is worth exploring in my opinion,” says, Dr. Hannah Gardener, a neurologist and researcher at the University of Miami. “The intra-uterine environment has profound effects on so many aspects of health throughout the lifecourse.”

It is true that autism existed long before the obesity epidemic, and most overweight or obese parents will never have a child diagnosed with autism. Conversely thousands of children born to normal weight parents will be diagnosed with autism this year. It is not likely that obesity is solely responsible for the increased rates of autism seen over the last three decades.

But have you ever been looking for your sunglasses, or reading glasses, only to find them sitting on the top of your head? I have, and now that’s the first place I check. The simultaneous evolution and parallel course of these two epidemics points to a connection that deserves to be investigated.

Sean Kenniff, MD is a neurologist, television health journalist, radio host and author living in Miami, Florida. He can be reached at 786-360-2705. 

Jacob Seligsohn, MD is a pediatrician in Hollywood, Florida. He can be reached at 954-966-8000, or by visiting the Pediatric Associates website at www.pediatricassociates.com 

Dr. Hannah Gardener is a neurologist and researcher at the University of Miami. She can be reached at 305-243-9283, or by visiting the University of Miami Miller School of Medicine Website at www.med.miami.edu