Alzheimer's Disease Risk increases if both Parents have Disease

In adulthood, the children of parents who have both been diagnosed with Alzheimer's disease have an increase risk of developing the disease, as reported in the March 2008 issue of the Archives of Neurology, which is one of the JAMA/Archives Journals.

Alzheimer's disease is a terminal, neurodegenerative disorder that commonly affects patients over 65 years old. "Alzheimer's disease is a common cause of dementia in the U.S. population and the leading cause of cognitive impairment in the elderly population," states the article.

Additionally, because there is a strong genetic component to the disease, the identification of genes involved in Alzheimer's disease is an important step towards detecting others at risk for the condition. "Because Alzheimer's disease is so common in the general population, it is not uncommon for both spouses to develop the disease. Offspring of two such affected individuals would presumably carry a higher burden of these Alzheimer's disease-associated genes." One such gene whose mutation has shown to be linked with Alzheimer's codes for the protein apolipoprotein E.

To this end, Suman Jayadev, M.D., of the University of Washington, Seattle, and colleagues examined the number of instances of Alzheimer's disease in the adult children of 111 families in which both parents had a clinical diagnoses of the disease. They also noted the age at which the onset of dementia occurred.

Suman Jayadev, M.D., of the University of Washington, Seattle, and colleagues studied the frequency of Alzheimer's disease in adult children of 111 families in which both parents had been clinically diagnosed with the disease. Ages at onset of dementia were also noted.

There were 297 offspring who reached adulthood. The following statistics were found, and are shown in contrast with the statistics available for the general population:

* 22.6 % developed Alzheimer's disease (estimated 6%-13% in the general population)
* 66.3 years was the average age at onset for the children
* There was a 31% increased risk for children older than 60 years
* There was a 41.8% increased risk for children older than 70 years

It is notable that at the time of the study, not all of the unaffected individuals had reached 70 years old, so this statistic may be underestimated. The authors write: "Of the 240 unaffected individuals, 189 (78.8 percent) had not yet reached age 70 years, suggesting that the incidence of Alzheimer's disease (22.6 percent) is an underestimation of the final incidence rate of Alzheimer's disease in this population."

Additional family members may present with Alzheimer's disease, but this did not increase the risk of developing the disease. It did, however, indicate a younger age of onset, for those who developed the illness. That is, children with no history of the disease beyond the parents had an older age at onset (72 years) compared with having one parents with a family history of the disease (60 years) or both parents with a family history (57 years.)

The authors conclude stating that such children in whom both parents have suffered from Alzheimer's are at a higher risk for the disease. "The role of family history and the specific genes involved in this phenomenon require a better definition," they say. "Families with a significant Alzheimer's disease history may be more likely to be referred to an Alzheimer's disease research center and, thus, the present patients may be 'enriched' for a particularly Alzheimer's disease-prone subgroup. Following these families as the offspring continue to age will provide increasingly informative data."

See Full Article