March 24, 2008 (MEDSCAPE) — A study shows that children of parents who both have Alzheimer's disease (AD) appear to be at a higher risk for the development of the disease than would be expected in the general population.

The study observed the offspring of couples in whom both partners had Alzheimer's disease and found that among those who survived to adulthood, the disease developed in more than 22% vs estimated rates of 6% to 13% in the general population.

"The role of family history and the specific genes involved in this phenomenon require a better definition," the researchers, with first author Suman Jayadev, MD, from the University of Washington in Seattle conclude.

Their report is published in the March issue of the Archives of Neurology.

Because Alzheimer's disease is so common in the general population, it is not uncommon for the disease to develop in both spouses, the study authors write. Offspring of 2 such affected individuals would be expected to carry a higher burden of Alzheimer's disease-associated genes, they note.

"Consequently, children of these spouses want to know their risk of AD and whether they have a greater risk than the general public," they write.

Previously, this group of investigators reported results from a pilot study of 31 conjugal spouse pairs with Alzheimer's disease, suggesting there was a higher risk, but most of the children at the time were younger than 50 years. In the present study, the investigators enlarged the group to include 111 conjugal pairs, both of whom were clinically diagnosed with AD, and in this analysis, more than 83% of the offspring were older than 50 years.

The 111 couples had 297 children surviving to adulthood. Of these, AD had developed in 22.6%.

The risk for AD increased with age, affecting 31.0% of those older than 60 years (58/187 offspring who have reached this age) and 41.8% of those older than 70 years (41/98).

"Of the 240 unaffected individuals, 189 (78.8%) had not yet reached age 70 years, suggesting that the incidence of Alzheimer's disease (22.6%) is an underestimation of the final incidence rate of Alzheimer's disease in this population," the study authors write. 

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