Monday, February 08, 2010

Autism risks detailed in children of older mothers

A woman's chance of having a child with autism increase substantially as she ages, but the risk may be less for older dads than previously suggested, a new study analyzing more than 5 million births found.

"Although fathers' age can contribute risk, the risk is overwhelmed by maternal age," said University of California at Davis researcher Janie Shelton, the study's lead author.

Mothers older than 40 were about 50 percent more likely to have a child with autism than those in their 20s; the risk for fathers older than 40 was 36 percent higher than for men in their 20s.

Even at that, the study suggests the risk of a woman over 40 having an autistic child was still less than 4 in 1,000, one expert noted.

The new research suggests the father's age appears to make the most difference with young mothers. Among children whose mothers were younger than 25, autism was twice as common when fathers were older than 40 than when dads were in their 20s.

The findings contrast with recent research that suggested the father's age played a bigger role than the mother's. Researchers and other autism experts said the new study is more convincing, partly because it's larger. Older mothers are known to face increased risks for having children with genetic disorders, and genes are thought to play a role in autism.

The study was released Monday in the February issue of the journal Autism Research.

Maureen Durkin, a University of Wisconsin researcher who also has studied the influence of parents' age on autism, said it's important to note that the increased risks are small and that most babies born to older mothers do not develop autism.

Durkin said the overall low risk for autism "may be the most important take-home message," especially for prospective parents

The study was based on records of all 5.6 million births in California between Jan. 1, 1990 and Dec. 31, 1999, and on cases of autism diagnosed before age 6. That number totaled more than 13,000; the study involved 12,159 autistic children for whom information on both parents' ages was also available.

The researchers took into account factors that might affect autism diagnosis, including parents' education and race.

Catherine Lord, director of the University of Michigan's Autism and Communication Disorders Center, said the study is stronger than previous research focusing on paternal age, and "gives us a fuller picture of what is going on."

Autism is a developmental disorder that involves mild to severe problems with behavior, communication and socializing.

Recent data suggest about 1 in 100 U.S. children are autistic, a rate that appears to have increased substantially in recent decades. Many experts believe that rise reflects better awareness and a broadening of the definition of autism rather than a true increase in affected children.

Births to older mothers also have risen in recent years, but that likely only accounts for a small part of the increase in cases, said study co-author and UC-Davis researcher Irva Hertz-Picciotto.

Dr. Edwin Cook, an autism researcher with University of Illinois at Chicago, offered a novel theory for why autism is more common among children with older parents: Autism is known to run in families and it may be that adults with mild or undiagnosed autism have children at later ages, Cook said.

The study doesn't include information on autism in adults.


Monday, February 01, 2010

Doc Who Tied Vaccine to Autism Ruled Unethical

In 1998, Andrew Wakefield, a gastroenterologist at London's Royal Free Hospital, published a study in the prestigious medical journal Lancet that linked the triple Measles, Mumps and Rubella (MMR) vaccine with autism and bowel disorders in children. The study - and Wakefield's subsequent public statements that parents should refuse the vaccines - sparked a public health panic that led vaccination rates in Britain to plunge.

Wakefield's study has since been discredited, and the MMR vaccine deemed to be safe. But now medical authorities in the U.K. have also ruled that the manner in which Wakefield carried out his research was unethical. In a ruling on Jan. 28, The General Medical Council, which registers and regulates doctors in the U.K., ruled that Wakefield acted "dishonestly and irresponsibly" during his research and with "callous disregard" for the children involved in his study. (See the year in health 2009.)

After the finding, Wakefield, who now heads an autism research center in Austin, Texas, described the decision as "unfounded and unjust." He added that he had "no regrets" over his work.

The General Medical Council, which will now decide whether to revoke Wakefield's medical license, highlighted several areas where Wakefield acted against the interest of the children involved in the 1998 study. It criticized Wakefield for carrying out invasive tests, such as colonoscopies and spinal taps, without due regard for how the children involved might be affected. It also cited Wakefield's method of gathering blood samples - he paid children at his son's birthday party $8 to give blood - and said that Wakefield displayed a "callous disregard for the distress and pain the children might suffer."

The panel also criticized Wakefield for failing to disclose that, while carrying out the research, he was being paid by lawyers acting for parents who believed their children had been harmed by the MMR jab.

The panel's ruling follows a refutation of Wakefield's research from the scientific community. Ten of 13 authors in the Lancet study have since renounced the study's conclusions. The Lancet has said it should not have published the study in the first place, and various other studies have failed to corroborate Wakefield's hypothesis. (Watch a video on the story of an uninsured woman.)

Despite this, the effects of the media frenzy surrounding Wakefield's research - a study found that MMR was the most written about science topic in the U.K. in 2002 - continue to be felt in Britain. Vaccination rates among toddlers plummeted from over 90% in the mid-1990s to below 70% in some places by 2003. Following this drop, Britain saw an increase in measles cases at a time when the disease had been all but eradicated in many developed countries. In 1998, there were just 56 cases of the disease in England and Wales; by 2008 there were 1,370.

Despite assurances from various health bodies that Wakefield's study was seriously flawed, he still has a dedicated following among parents concerned about a rise in autism rates in the U.K. and U.S. - the cause of which has so far baffled health experts. Wakefield is now the Executive Director of the Thoughtful House autism center in Texas, which the Times of London recently claimed receives millions of dollars in donations each year. At the ruling in London, Wakefield was flanked by a small group of supporters, some of whom shouted in protest as the ruling was read out. Speaking after the hearing, Wakefield remained unbowed, and addressed his supporters directly: "It remains finally for me to thank parents whose loyalty has been extraordinary, and I want to reassure them that the science will continue in earnest."


Tuesday, January 12, 2010

Ongoing Evolution May Explain Mysterious Rise in Diseases

While natural selection is best known for weeding out the weak, it may also be partly responsible for the apparent rise of some disorders, such as autism, autoimmune diseases and reproductive cancers, according to researchers.

Since evolutionary factors play a role in disease, the two fields should have some crossover, say a group of scientists who have studied various aspects of the link between evolution and medicine.

"This work points out linkages within the plethora of new information in human genetics and the implications for human biology and public health, and also illustrates how one could teach these perspectives in medical and premedical curricula," said researcher Peter Ellison, an anthropologist at Harvard University.

The results, they say, could save lives.

"Evolutionary medicine got going in the '80s and early '90s, but it has been energized in the last decade by the discovery that it really makes a difference," researcher Stephen Stearns of Yale University told LiveScience. "In the last 10 years we have found out that taking an evolutionary perspective really helps to reduce suffering and to reduce the risk of death."

Evolution and disease

Stearns and a long list of scientists presented their findings on this evolution-medicine link at the Arthur M. Sackler Colloquium in the spring of 2009. The results, announced publicly today, are now published in the journal Proceedings of the National Academy of Sciences.

For example, previous work in evolutionary medicine has helped to explain some reasons why disease is so prevalent and difficult to prevent: Natural selection favors reproduction over health; biology evolves more slowly than culture; and pathogens evolve more quickly than humans.

They describe these and other connections between evolution and sickness along with possible explanations. Here are the highlights:

  • Humans evolved alongside beneficial bacteria and parasitic worms, and so our ancestors built up immunity to such bugs. But nowadays with increased hygiene, we've eliminated the bacteria and worms. The result: Since our immune systems aren't used to these good bugs, our bodies fight them as foreigners. That can result in allergies, asthma and autoimmune diseases, such as Graves' disease in which a person has an overactive thyroid.
  • Humans have higher rates of cancer than other species. One reason: We aren't adapted to the new risk factors of modern society, including tobacco, alcohol, a high-fat diet and contraceptives, researchers have found.
  • Certain adaptations that once benefited us might be helping several ailments to persist in spite of, or perhaps because of, advancements in modern culture and medicine, according to researchers.

With respect to evolution and culture, here's a case in point: Harmful mutations are often recessive, and so both parents must pass on the gene in order for the disease to show up in offspring. And while natural selection has supported outbreeding (breeding with people other than close relatives), culture hasn't always followed suit. Across the globe, about 10 percent of spouses are second cousins or closer, the researchers say, with the prevalence ranging from 1 percent to 50 percent in different cultures.

The inbreeding can cause recessive genes that should only have a small effect on mortality to have a much larger impact.

Autism and evolution

Autism and schizophrenia also have ties with evolutionary science. Essentially, they boil down to a battle of the sexes.

Past studies beginning in the 1960s have built on one another to suggest mom and dad are in evolutionary conflict over investment of resources to their offspring. A mother knows all of her babies are hers and so should give evenly to all. But fathers only want to invest in their biological kids (not offspring from another male) and so a father's genes will pressure mom to skew investment toward those offspring.

Studies in genetically engineered mice have shown that when certain paternal genes get expressed, the baby mice are 10 percent heavier than normal.

The results should translate to humans and carry into early childhood, affecting children's behaviors, the researchers suggest.

For instance, when the paternal form of a gene on chromosome 15 gets expressed, and not the mother's, the resulting offspring will be more demanding, sleep poorly, want to suckle frequently and have a 40 percent to 80 percent chance of having autism as an adult. (Humans normally have 46 chromosomes in each cell.) While scientists think genes play a role in developing autism, the complex causes of this disease are still unknown.

Similar findings have shown psychoses such as schizophrenia can develop when the maternal form of certain genes gets expressed.

Educating physicians on evolution

Stearns suggests evolutionary perspectives should be integrated into curricula as early as undergraduate school for students planning to attend medical school. The knowledge, Stearns said, would complement traditional studies undertaken in medical school.

We're trying to design ways to educate physicians who will have a broader perspective and not think of the human body as a perfectly designed machine," Ellison said. "Our biology is the result of many evolutionary trade-offs, and understanding these histories and conflicts can really help the physician understand why we get sick and what we might do to stay healthy."

The take-home message: "Evolution and medicine really do have things to say to each other, and some of these insights actually reduce suffering and save lives," Stearns said.