Knowing the incidence of dementia in first-degree relatives, as well as distant family members, may indicate an individual's risk of Alzheimer's disease.
Researchers from the University of Utah School of Medicine suggest that chances of developing Alzheimer's are high even if the parents, siblings, or children are unaffected. Predicting outcomes can help clinicians prescribe preventive measures instead of aggressive treatments that could worsen the symptoms.
The risk of having Alzheimer's disease is doubled when a person has one close relative and one distant relative who have the same disease. If the incidence of Alzheimer's disease is present in at least one first-degree and two second-degree relatives, the risk increases by 21 times.
"Family history is a very powerful piece of information that can accurately predict someone's risk of Alzheimer's disease, and this study shows there are more people at risk than we know," said lead author Lisa Cannon-Albright, an epidemiology professor at UUSOM.
The study analyzed death certificates of more than 270,000 people in Utah dating back to the 1800s. About 4500 of those people had Alzheimer's disease.
Having a parent or a sibling with Alzheimer's increases the risk of developing the disease by 73 percent. The odds are quadrupled if there are two first-degree relatives with the same disease.
Although the association of family history Alzheimer's incidence is interesting, the authors noted that it was not the cause of death in the majority of the cases they followed.
An Expected Reality
Rebecca Edelmayer, Alzheimer's Association director of Scientific Engagement, said the results of the study are not unique. However, it could provide additional information to look outside the first-degree population.
Men with one or more affected first-degree relatives are more at risk compared to women. The same is true for men with one or more second-degree but no affected close relatives. Similarly, affected individuals from the maternal side pose a greater risk to their close or distant relatives compared to the paternal side.
"This is a surprising observation," said co-author John Kauwe, professor and chair of the biology department at Brigham Young University. "However, the overall evidence for paternal, versus maternal, inheritance in our data is mixed. We will need additional analysis in this and other datasets to be more certain about these results."
The study was published in the journal Neurology.