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

What is Worse? This or That?

What’s Worse, This or That?

by Sean Kenniff, MD 

What is worse: being obese or suffering from anorexia nervosa? 

Statistics show anorexia nervosa has the highest fatality rate of any psychological disorder. Up to twenty-percent of those affected will die from the condition if left untreated, and roughly three-percent die even with therapy. Obesity also kills, but much more slowly. The mortality rate for people suffering from anorexia nervosa is higher, and they tend to die at much younger ages when compared to an obese people of the same age. For an obese twenty-five-year old woman the risk of dying is around 0.1%.

What is worse for parents with children: Having a gun in the house, or a swimming pool in the backyard?

In the book Freakonomics by economist Steven Leavitt, statistical analysis reveals that having a swimming pool is roughly 100-times more risky than having a gun in the house. According to Leavitt there are 6-million residential swimming pools in the U.S., and more than 500 children drown in them each year-so roughly one child drowns for every 11,000 swimming pools. Meanwhile there are more than 200-million guns in the U.S., but fewer than 200 deaths in children under the age of ten are due to firearms. Simple math tells you that the risk of having a gun in the home is just 1-child death for every 1-million guns.

What is worse: smoking marijuana cigarettes, or smoking tobacco cigarettes?

This question appeared in an editorial in the British Medical Journal in 2003. From a legal point of view marijuana is certainly worse. But when it comes to your health tobacco cigarettes are a much bigger risk. Two large studies failed to find an increased risk of death associated with cannabis use. While there are plenty of carcinogens in marijuana smoke, people do not tend to chain-smoke the drug-so the overall exposure to those carcinogens is much less. And most marijuana smokers cease smoking the drug in early adulthood. Cigarettes pose a much larger personal and public health risk. However this conclusion comes with a caveat: perhaps the main reason people stop smoking marijuana after a certain age is because of its illegality. As we age we are less likely to commit these kinds of criminal activities. Decriminalization of marijuana may lead to more prolonged smoking and perhaps more deaths. But overall cigarettes are much worse. In the United States tobacco use contributes to roughly 1-in-5 deaths.

What is worse: being married and miserable, or happy and single? 

Research shows happily married couples live longer than singles, and the health benefit of being in a happy marriage is more profound for men than it is for women. People in positive marital relationships have lower blood pressures and reduced levels of stress hormones when compared to unhappily married couples. And a recent study from BYU researchers found unhappily married people have a higher blood pressure, and higher stress hormones than happy singles and happily married folks. So being unhappily married appears to pose the biggest risk to your health. But before you think about heading to divorce court, several studies have shown divorce can increase the risk of death. So try to make your marriage a happy one. 

It’s also important to mention that overall never-married people face the highest risk of death (unhappy and happy singles combined). A study published in 2006 found never-married people faced 5-times the risk of dying from infectious diseases, were 38-percent more likely to die from heart disease, and faced twice the risk of dying from an accident, homicide, or suicide.

What is worse: air pollution or being exposed to second-hand smoke?

Air pollution from industrial pollutants and motor vehicles accounts for 3% of all U.S. deaths according to an article in the European Respiratory Journal. A study from University of Southern California in 2007 found children living near a major highway (within 500 meters) were more likely to have asthma, other respiratory diseases, and were more likely to have reduced lung function and reduced lung growth. Living close to a busy highway has also been associated with an increased risk of heart disease and some cancers. Air pollution alone causes between 22,000 and 55,000 deaths each year in the U.S. according to government statistics, but the National Resources Defenses Council says air pollution is responsible for 64,000 deaths each year. Particulate matter and benzene are thought to be playing the largest role in causing the health problems. 20-million Americans live under air pollution that contains more than 32 toxins at levels 100 times higher than the EPA deems acceptable. The World Health Organization says worldwide there are 2-million deaths due to air pollution each year. So how does second-hand smoke compare? The American Cancer Society estimates exposure to second-hand smoke causes roughly 3400 lung cancer deaths and between 22,000 and 69,000 deaths from cardiovascular disease each year in the U.S. There are approximately 21-million American children (35%) living in homes where they are exposed to second-hand smoke. So the numbers turn out to be roughly the same.