Offspring of parents who both have Alzheimer's disease may be more likely to develop the illness

Adult-age offspring of parents who have both been diagnosed with Alzheimer's disease appear to have an increased risk of developing the disease compared with the general population, according to a report in the March issue of Archives of Neurology.

“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,” according to background information in the article. Identifying genes in Alzheimer's disease patients can help detect others who are 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.”

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.

Of the 297 offspring who reached adulthood, 22.6 percent developed Alzheimer's disease compared with an estimated 6 percent to 13 percent of the general population. The average age at onset for children of couples with the illness was 66.3. The risk of developing the disease increased with age with 31 percent of those older than age 60 affected and 41.8 percent of those older than age 70 affected. “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,” the authors write.

Having additional family members with Alzheimer's disease did not increase the risk of developing the disease, but was associated with a younger age at onset for those who did develop the illness. Children with no history of the disease beyond the parents had an older age at onset (72 years) compared with those who had one parent with family history of the disease (60 years) or both parents with family history of the illness (57 years).

“The role of family history and the specific genes involved in this phenomenon require a better definition,” the authors conclude. “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.”

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