Public release date: 25-Sep-2007

MEDFORD/SOMERVILLE, Mass. — For years researchers in neurology have believed that people with Huntington’s disease have more children than the general population because of behavioral changes associated with the disease that lead to sexual promiscuity. In a new Tufts University study, three biologists have challenged that notion by suggesting that people with Huntington’s have more children because they are healthier – not more promiscuous – during their peak reproductive years. “A Darwinian Approach to Huntington’s Disease: Subtle Health Benefits of a Neurological Disorder” is published in the August 8, 2007 online issue of the journal Medical Hypothesis and will soon appear in print.

The Tufts team analyzed the often-noted fertility gap between people who have Huntington’s and those who do not. Studies comparing family members indicated that individuals with the disease had between 1.14 and 1.34 children for every child born to an unaffected sibling. In explaining this difference, previous researchers have theorized that psychological deterioration and difficulty in discriminating between right and wrong – both symptoms associated with Huntington’s – are reasons for promiscuous behavior in people who had the disease. But Eskenazi, Wilson-Rich and Starks observed that such behavior takes place later in life – not during peak reproductive age. They noted that the onset of Huntington’s disease occurs, on average, at 41.5 years of age.

Starks and his team suggested that one key factor behind these health benefits may be p53, and pointed to a 1999 study by doctors at the Danish Huntington Disease Registry at the University of Copenhagen that found lower age-adjusted cancer rates for individuals affected by Huntington’s. “Research has shown that individuals with Huntington’s produce higher levels of cancer-suppressing p53, and we hypothesize that they may also reap the health benefits associated with a generally more vigilant immune system,” said Starks. “These individuals also suffer from the negative impacts of heightened immune function, as they are more likely than those without Huntington’s to suffer from autoimmune diseases.”

Starks, whose research areas include behavior and evolution in a wide range of organisms, noted that Huntington’s disease may be an example of antagonistic pleiotropy, in which one gene creates multiple and conflicting effects. Another example of this phenomenon includes a gene that appears to decrease the incidence of Alzheimer’s disease while increasing the chance of elevated lipids in the blood. The convergence of evolutionary biology and medicine can reap many benefits, he believes. “This marriage has already shed light on phenomena such as fever and morning sickness,” he noted. Huntington’s disease may be one more beneficiary of this synergy.