Alzheimer's Risk Tied to Uncles, Aunts, and Great-Grandparents With the Disease

Having cousins and great-grandparents with Alzheimer's has been linked to a higher risk of developing the disease, according to a study.

Scientists looked at the data on over 278,818 people included in the Utah Population Database, stretching back to the 1880s, for their work published in the journal Neurology. The participants were connected to the state's pioneers by at least three generations.

The information was linked to death certificates detailing how the individual died. A total of 4,436 people had Alzheimer's disease listed as a primary or contributing cause of their death.

The team found there was an association between Alzheimer's disease and whether second and third-degree relatives—such as blood-related grand- and great-grandparents, aunts, uncles, great aunts and uncles, cousins and siblings with one shared parent—had the condition.

More specifically, an individual with three third-degree relatives—for instance no parents but a great uncle and two great-grandparents with Alzheimer's—had a 43 percent higher chance of developing the condition from the baseline.

And a person with one parent or sibling with Alzheimer's appeared to have a 73 percent chance of developing the disease. Those with three first-degree relatives with the disease had a 2.5 times higher chance, while those with two were four times more likely to have the condition.

Dr. Lisa A. Cannon-Albright, study co-author at the University of Utah School of Medicine in Salt Lake City, explained family history is one indicator of whether a person is vulnerable to developing Alzheimer's, but few studies have focused on members outside the immediate circle.

"We learned that both close and distant family history affects estimates of risk and should be used if possible," she told Newsweek.

"It was surprising that even if the closest relatives known to be affected are third degree (e.g. first cousins), your risk is still elevated over population rates," she said.

However, the study's findings were limited because the authors relied on the condition being noted as a cause of death on the death certificate, which comes down to the discretion of individual healthcare professionals. Cases of Alzheimer's disease in the cohort were likely underestimated, the authors said.

Dr. Sara Imarisio, a head of research at the charity Alzheimer's Research UK who was not involved in the study, said: "While in some rare instances—less than 1 percent of all people who develop Alzheimer's—the disease is caused by an inherited genetic mutation, this is not the case for the vast majority of cases.

"Developing Alzheimer's disease is usually due to a complex mix of age and other modifiable risk factors. If a close family member has Alzheimer's it does not mean you will also develop the disease.

"This research looks at a group of people with rich information about their family history and as scientists have identified around 30 genes that are linked to Alzheimer's risk, it is no surprise that this study identified an association between an individual's risk of the disease and having relatives who died from Alzheimer's.

She continued: "The best current evidence suggests that not smoking, drinking within recommended guidelines, staying physically and mentally active, eating a healthy balanced diet and keeping cholesterol and blood pressure in check are all good ways to support a healthy brain as we age."

A separate study published earlier this week found what a person eats in middle age doesn't affect their risk of developing dementia as they grow old.

However, Dr. James Pickett, head of research at the charity Alzheimer's Society and who was not involved in the research, stressed keeping a healthy diet was still advisable. He recommended ditching snacks like chips and substituting fruit, keeping active, and not smoking to not only cut the risk of heart disease, cancer and stroke, but also to keep the brain healthy.

This article has been updated with comment from Dr. Lisa Cannon-Albright.