A genetic study of Alzheimer’s disease that its authors describe as the largest to date has identified 127 regions of human DNA linked to the risk of developing the disease, 48 of them newly mapped. The analysis, published Oct. 28 in Nature, drew on genetic data from about 2.8 million people, including 183,620 with Alzheimer’s.

The strongest biological signal pointed to microglia, the brain’s immune cells, which clear away harmful substances and damaged cell material. The findings also implicated several specific types of neurons and processes involving amyloid, the protein that forms plaques in Alzheimer’s.

For families, the result is a research milestone, not a new test or treatment. The researchers stress that these genetic associations are a starting point for drug research and do not show which genes cause the disease.

Microglia and Neurons at the Center

The study was carried out under the Psychiatric Genomics Consortium, whose Alzheimer’s disease working group is co-led by Danielle Posthuma of Vrije Universiteit Amsterdam and Ole Andreassen of the University of Oslo. It pooled data from 30 research groups. Participants came from several ancestries, though most were of European descent.

The results reinforce the role of microglia in Alzheimer’s risk, including processes tied to their activation, the recruitment of immune cells, and the clearance of material in the brain. According to Vrije Universiteit Amsterdam, the study also found genetic links to amyloid processing, nerve cell repair, the activation of support cells called astrocytes, and maintenance of myelin, the insulation around nerve fibers. For the first time, the researchers identified several specific types of neurons enriched for genetic risk signals.

“We already knew that immune processes play an important role in Alzheimer’s disease,” said Posthuma, who led the research, in a statement shared by the University of Exeter, which contributed data. She said the study connects new genetic risk factors “to more specific biological processes, while also uncovering evidence pointing to the involvement of other brain cell types.”

The researchers said the findings can guide laboratory models and help identify genes that may be worth testing as drug targets.

The team also estimated that common genetic variants explain about 16% of population-level differences in Alzheimer’s risk, nearly three times an earlier estimate of about 5%. Much of that increase comes from a statistical method that better accounts for APOE, the best-known Alzheimer’s risk gene.

Limits of a Genetic Association Study

This kind of study, called a genome-wide association study, finds DNA regions that are more common in people with a disease. It does not identify which gene in each region matters, how it acts, or whether changing it would help. The authors said follow-up research is needed to determine which associations are causal and whether targeting them is safe and meaningful.

The 16% figure is also easy to misread. “It does not mean that 16 percent of any one person’s Alzheimer’s is caused by their genes,” co-first author Emil Uffelmann said, adding that it also does not mean a genetic test can determine whether someone will develop the disease. Age, environment, and other factors also shape risk.

Part of the sample relied on “proxy” cases, people counted through a parent’s Alzheimer’s diagnosis rather than their own. In a preprint version of the study, an analysis limited to diagnosed cases and controls still found 95 significant regions. Proxy cases have drawn scrutiny before: discussing an earlier 2021 study that used a similar approach, Washington University in St. Louis geneticist Carlos Cruchaga told Alzforum that proxy cases make it harder to tell whether a signal is specific to Alzheimer’s or reflects other dementias.

Representation is another gap. The researchers called for more large-scale genetic research that includes underrepresented populations so that findings and future treatments apply to a broad range of people. That matters in the U.S., where older Black Americans are about twice as likely, and older Hispanic Americans about one and a half times as likely, to have Alzheimer’s or other dementias as older white Americans, according to the Alzheimer’s Association.

MedicalDaily Evidence Check: This is a peer-reviewed genetic association study of about 2.8 million people, published in Nature. It found 127 risk regions, 48 of them new, with signals concentrated in microglia and certain neurons. It did not prove that any gene causes Alzheimer’s, and it does not change diagnosis, screening, or treatment today.

Families, Caregivers, and the Long Road to Treatment

About 7.4 million Americans age 65 and older are living with Alzheimer’s in 2026, according to the Alzheimer’s Association. Almost two-thirds of Americans with Alzheimer’s are women, and health and long-term care costs for people with Alzheimer’s and other dementias are projected to reach $409 billion this year. In New York State, about 426,500 residents age 65 and older live with the disease, and 776,000 residents serve as unpaid family caregivers, according to the association’s 2026 state figures.

Moving from a genetic signal to an approved drug typically takes many years, and most drug candidates fail along the way.

Genetic testing is not the answer for most people right now. The researchers said their improved risk prediction models are mainly useful for research, and their use in clinical care is still being studied. Risk genes such as APOE raise the likelihood of Alzheimer’s but do not guarantee it, and the association advises that people considering genetic testing should receive genetic counseling before and after the test.

People noticing memory changes in themselves or a relative should see a clinician, because some causes of memory problems, such as thyroid problems, low vitamin B12, or medication side effects, can be treated. Families interested in research can ask a doctor about clinical trials. The next steps belong to laboratories testing which of the newly linked genes drive disease.

Key Questions Answered

What did the study find? It found 127 DNA regions linked to Alzheimer’s risk, including 48 not previously identified, using genetic data from about 2.8 million people, 183,620 of whom had Alzheimer’s.

What are microglia? They are the brain’s immune cells, which clear away harmful substances and damaged cell material. The study found that much of the genetic risk pointed to these cells.

Does this mean these genes cause Alzheimer’s? No. The study found associations. More research is needed to show which genes play a causal role.

Should I get a genetic test for Alzheimer’s? Not based on this study. Risk genes such as APOE raise the likelihood of Alzheimer’s but do not guarantee it. The Alzheimer’s Association advises genetic counseling before and after any test.

Will this lead to new treatments? Possibly in the long term. The findings point to potential drug targets, but drug development takes many years.

How many Americans have Alzheimer’s? About 7.4 million Americans age 65 and older in 2026, according to the Alzheimer’s Association.

Published by Medicaldaily.com