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Alzheimer’s Risk Skyrockets if Both Parents Have the Disease

March 11, 2008

Researchers at the University of Washington in Seattle reported Monday that a person’s risk of Alzheimer’s disease jumps dramatically if both parents have the disease.

The researchers performed a study with 111 families in which both parents had been diagnosed with Alzheimer’s disease, and then assessed the risk among the offspring of developing the disease.

In total, the parents had 297 children, of whom 98 were at least 70 years old.  The research found that of these 98 children, 41, about 42 percent, had developed Alzheimer’s disease.

“That’s greater than you would expect in the general population in that age group,” Dr. Thomas Bird, one of the researchers, said in a Reuters telephone interview.

During the study, approximately two-thirds of the adult children had not yet reached age 70. As a whole, the researchers found that 23 percent of all the adult offspring, regardless of age, had been diagnosed with Alzheimer’s disease at an average at age 66.

Bird said that equates to roughly a one in 10 chance of developing the disease.

“I think it confirms that there’s a strong genetic component in the disease and that’s not a surprise,” said Bird.

Bird said only one gene, known as ApoE, is generally acknowledged among experts as a risk factor for the disease, although there are likely many more.

The ApoE gene plays a role in producing a chemical in the body that helps carry cholesterol in the bloodstream, and appears to effect the age of onset of Alzheimer’s.

The study has been ongoing for the past two decades, with plans to continue for at least another decade. The researchers are not examining Alzheimer’s risk children who have only one parent with the disease.

“The numbers will be interesting to follow as they get older and older,” Bird said.

In confirming the presence of Alzheimer’s disease in both parents, researchers reviewed medical records, analyzed brain autopsies of those who had died, and when possible met with those still living with the disease.

Alzheimer’s disease is the most common form of dementia among the elderly. It results in the degeneration of healthy brain tissue, causing an inevitable decline of memory and mental abilities. The average length of time from diagnosis to death is about eight years.

Scientists do not fully understand the underlying cause of the disease, although genetics is believed to play an important role. There is no known cure. 

The risk of developing Alzheimer’s disease increases after age 65, with the number of people developing the disease doubling every five years thereafter.

The study was published in the journal Archives of Neurology.  A summary can be viewed at http://archneur.ama-assn.org/cgi/content/abstract/65/3/373.

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