March 13, 2019
2 min read

Risk for Alzheimer’s disease extends beyond immediate relatives

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Recent study results demonstrate that not only were individuals with first-degree relatives who had Alzheimer’s disease at higher risk for developing the disease, but those with affected second- and third-degree relatives were also at increased risk. Therefore, researchers recommend providers consider a broad family history when discussing risk with patients and their families.

"More and more, people are increasingly seeking an estimate of their own genetic risk for Alzheimer's disease," Lisa A. Cannon-Albright, PhD, of the University of Utah School of Medicine, said in a press release. "Family history is an important indicator of risk for Alzheimer's disease, but most research focuses on dementia in immediate family members, so our study sought to look at the bigger family picture.”

Using the Utah Population Database — which includes the genealogy of Utah pioneers from the 1800s and their descendants and is linked to Utah death certificates — researchers analyzed data from more than 270,800 people who had at least three generations of genealogy, according to the press release. They used these data to estimate risk for Alzheimer’s disease based on specific family history patterns, including from first- to third-degree relatives.

First-degree relatives include parents, offspring and siblings; second-degree relatives include grandparents, grandchildren, aunts/uncles and nieces/nephews; and third-degree relatives include great-grandparents, great-grandchildren, grand nieces/nephews, great aunts/uncles and cousins.

Overall, 4,436 individuals had Alzheimer’s disease as a primary or contributing cause of death.

The results showed that individuals with immediate relatives who had Alzheimer’s disease were at significantly higher risk for the disease:

  • one or more first-degree relatives (FDRs): RR = 1.73; 95% CI, 1.59–1.87;
  • two or more FDRs: RR = 3.98; 95% CI, 3.26–4.82;
  • three or more FDRs: RR = 2.48; 95% CI, 1.07–4.89; and
  • four or more FDRs: RR = 14.77; 95% CI, 5.42–32.15.

Furthermore, analysis revealed that people with one affected first-degree relative and one second-degree relative were at 21 times greater risk for Alzheimer’s disease (RR = 21.29; 95% CI, 5.8-54.52). Those who had three or more third-degree relatives with Alzheimer's disease had a 43%greater risk of developing the disease (RR = 1.43; 95% CI, 1.21-1.68), according to the study.

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"We found that having a broader view of family history may help better predict risk. Our findings indicate the importance of clinicians taking a person's full family history that extends beyond their immediate family members,” Cannon-Albright said in the release. “These results potentially could lead to better diagnoses and help patients and their families in making health-related decisions."

Given equivalent family history, men were at greater risk for Alzheimer’s disease than women, the researchers reported. In addition, the higher risk for Alzheimer’s disease was observed in individuals with at least one affected first-degree relative regardless of their age at death.

"There are still many unknowns about why a person develops Alzheimer's disease," Cannon-Albright said. "A family history of the disease is not the only possible cause. There may be environmental causes, or both. There is still much more research needed before we can give people a more accurate prediction of their risk of the disease." – by Savannah Demko

Disclosure: Cannon-Albright reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.