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An international study in Nature analyzed genetic data from nearly 2.8 million people and identified 127 Alzheimer’s disease risk loci, including 48 not previously reported. The researchers also found that one method estimated a greater contribution from common genetic variants than an earlier method did, but the study does not establish an individual’s risk or prove that proposed drug targets will work.
An international team analyzing genetic data from nearly 2.8 million people identified 127 genetic loci associated with Alzheimer’s disease, including 48 not previously reported, and found evidence that common genetic variants may account for more inherited risk than some earlier estimates suggested. The study, published in Nature, also linked Alzheimer’s genetic associations to microglial immune cells and neurons; it does not show that any proposed drug target is an effective treatment.
The researchers combined data from 30 cohorts, including people diagnosed with Alzheimer’s, people whose parent had Alzheimer’s or dementia, and control participants. The overall dataset included 109,479 people with Alzheimer’s, 74,141 proxy cases, 2,131,799 controls and 499,708 proxy controls. Proxy cases were participants who reported a parent with the disease; they were not counted as people with Alzheimer’s themselves. The study’s effective sample size was 416,493.
The analysis found 118 significant loci in its multi-ancestry analysis and nine additional loci in a European-ancestry-only analysis. In total, 48 of the 127 loci were newly identified. The researchers also identified 72 gene sets associated with the disease, including pathways related to lipid binding, immune activation, amyloid breakdown and cell adhesion.
For genetic contribution, the team used SBayesRC to estimate heritability from common genetic variants and compared its results with estimates from linkage disequilibrium score regression, or LDSC. The report says the methods produced different estimates, and simulations examined why they might differ. This speaks to how researchers estimate inherited risk across populations; it does not mean genes explain the same share of risk for every person.
Why revised risk estimates matter
How much Alzheimer’s risk is attributed to inherited variation affects risk prediction and the design of genetic studies. If commonly used methods miss some genetic contribution, researchers may be underestimating the role of inherited factors or overlooking associated biological pathways. The findings give investigators a broader set of candidate regions and processes to study.
The cellular results also point beyond a single explanation of Alzheimer’s biology. Associations were enriched among genes preferentially expressed in microglia, immune cells in the brain, and among genes expressed in several neuronal populations. The microglial signal remained significant after the researchers adjusted for average differences in gene expression across cell types; the neuronal associations became nominal rather than statistically significant. This suggests the microglial result was more robust in that particular analysis.
The study’s treatment implications are preliminary. Researchers highlighted RRM2B, SYK, KEAP1, CACNA1S and AXL as possible drug targets, but did not test them as treatments. Some prior experimental findings were described as promising, while interventions involving CACNA1S and AXL had not improved outcomes in cited human and mouse studies. A genetic association alone does not establish that changing a gene or its activity would safely prevent or treat Alzheimer’s.
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How the study revisits heritability
Twin studies have estimated that 60% to 80% of susceptibility to Alzheimer’s is heritable. Earlier genome-wide association studies had identified about 80 risk loci, while estimates based on common single-nucleotide polymorphisms suggested those variants accounted for roughly 5% of disease liability. These figures are not interchangeable: they draw on different methods and describe different aspects of genetic contribution.
Alzheimer’s disease is the most common form of dementia. The study’s authors frame its genetic analysis against a treatment landscape in which disease-modifying drugs primarily target amyloid-beta aggregates, with limited effectiveness in relieving symptoms. They also examined the gene QPCT, connecting it to an amyloid-beta modification targeted by donanemab. That genetic analysis does not itself establish donanemab’s effectiveness or alter its clinical evidence.
The study included participants grouped by European, African, East Asian, admixed American and South Asian ancestry. However, about 91% of the effective sample was of European ancestry. The authors reported that results were less precise in ancestry groups with smaller samples, limiting how confidently the findings can be compared across groups.
“The study investigated whether existing methods underestimate the genetic contribution to Alzheimer’s disease.”
— The study’s researchers, as described in the News-Medical report
Limits of the genetic evidence
The findings do not settle how much of Alzheimer’s risk is inherited. Heritability estimates depend on the method and the population studied, and the report does not provide a single definitive estimate applicable to everyone. It also does not establish how the newly identified loci affect disease biology or how much each contributes to risk.
Representation across ancestry groups is uneven: European-ancestry participants accounted for about 91% of the effective sample. Results for groups with smaller samples were less precise, so the study offers a limited basis for comparing genetic risk across ancestries. The proxy cases, based on parental disease reports, also differ from confirmed diagnoses in participants themselves.
The researchers found expression-related signals in microglia and neurons, but the study cannot determine whether neuronal expression differences help cause Alzheimer’s or arise after neurodegeneration. No individual microglial state reached statistical significance, and the proposed drug targets remain candidates rather than tested therapies.
What researchers need to test
Further work will need to replicate the associations, particularly in ancestry groups that were less well represented, and establish how the implicated genes and pathways affect disease processes. The researchers’ results offer candidates for functional studies, but the supplied report does not specify a next study or a timeline for follow-up.
Any move toward treatment research would require testing whether modifying a proposed target changes disease outcomes and whether the intervention is safe. Separately, researchers would need to validate whether the findings improve risk prediction in independent populations. For now, the confirmed development is a larger set of genetic associations and a method-dependent reassessment of inherited contribution—not a new clinical test or Alzheimer’s treatment.
Key Questions
What did the Alzheimer’s genetics study find?
It identified 127 associated genetic loci, including 48 not previously reported, and linked Alzheimer’s genetic associations to pathways involving microglia, neurons, immune activity and other processes.
Does the study prove that genes cause Alzheimer’s?
No. It examines genetic associations and estimates inherited contribution. It does not show that genes alone cause the disease or determine an individual’s outcome.
Does this mean Alzheimer’s risk is higher for everyone?
No. The study does not establish a higher personal risk for any individual. Its findings concern population-level genetic analysis, and estimates depend on methods and the groups represented in the data.
Are the proposed genes new Alzheimer’s treatments?
No. RRM2B, SYK, KEAP1, CACNA1S and AXL were highlighted as possible targets, but the researchers did not test them as treatments in this study.
How representative was the study across ancestry groups?
The analysis included five ancestry groupings, but about 91% of its effective sample was of European ancestry. The researchers said results were less precise in groups with smaller samples.
Source: news-medical.net
