A recent study suggests that adults who have two parents who have been diagnosed with Alzheimer’s disease are more likely to develop the disease themselves and to do so at an earlier age than those without.

Lead research scientist Suman Jayadev, MD, of the University of Washington in Seattle, and colleagues studied all 297 children of 111 families where both parents had been diagnosed with Alzheimer’s disease. The study measured the number of children who developed the disease themselves and the age when the disease began.

Of the 297 offspring, 22.6% eventually developed the disease themselves whereas the incidence of the disease in the general population ranges from 6% to 13%. In the children of couples with Alzheimer’s, the rate of developing the disease increased as the children aged. Average age of onset within the study group proved to be 66.3 years.

Thirty-one percent of the study subjects developed Alzheimer’s disease after the age of 60 and 41.8% developed it after the age of 70. As of this time, 189 of the study participants (78.8%) have not yet reached the age of 70 themselves, leading researchers to suggest the current rate of incidence (22.6%) may be an underestimation of the actual rate of disease within this group, with more cases of the disease showing up as the study group ages.

In the general population, the average age of onset when there is no parental history of the disease is 72. When one parent is diagnosed, onset in offspring begins at an average age of 60. When both parents have the disease, the age of onset in their children is an average of 57.

The research team suggests that families affected by Alzheimer’s disease are more likely to be referred to research centers than those not affected. The referral process may have an effect on research by theoretically enriching the populations being studied as opposed to the actual rate of the disease in the general population. More research is suggested to more clearly define the role of genetics and family history in the general population. The families of couples with the disease will continue to be monitored as they age further.

The March 1 edition of the Journal of the American Medical Association (JAMA) and Archives Journal carries the full details of the study.