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An international study drawing on genetic data from nearly 2.8 million people identified 127 Alzheimer’s disease risk loci, including 48 not previously reported. The researchers also found that estimates of genetic contribution varied by method, suggesting earlier approaches may have understated the role of common variants; the findings do not establish individual risk or prove proposed drug targets will work.
An international research team has identified 127 genetic loci associated with Alzheimer’s disease using data from nearly 2.8 million people, and reports that common genetic variants may contribute more to disease risk than some earlier estimates suggested. The study, published in Nature, also links genetic associations to immune activity in microglia and changes in neurons, but does not show that any of its proposed drug targets are effective treatments.
The researchers combined data from 30 cohorts, including people diagnosed with Alzheimer’s, proxy cases whose parent had Alzheimer’s or dementia, and control participants. The full dataset included 109,479 people with Alzheimer’s, 74,141 proxy cases, 2,131,799 controls and 499,708 proxy controls. The study’s effective sample size was 416,493, and about 91% of that effective sample was of European ancestry.
The multi-ancestry analysis found 118 significant risk loci; a separate analysis of European-ancestry participants identified nine more, for 127 overall. Forty-eight were new findings, according to the study. The team also identified 72 significant gene sets, with results pointing to processes involving lipid binding, immune activation, amyloid breakdown and cell adhesion.
To estimate inherited contribution, the investigators used SBayesRC and compared its results with estimates from linkage disequilibrium score regression. The study’s title and analysis highlight the possibility that earlier methods understated the contribution of common variants. The source report does not provide a revised heritability percentage, so the findings should not be read as a new, definitive estimate of how much Alzheimer’s risk is genetic.
What the Genetic Findings Could Change
A clearer map of genetic associations could help researchers investigate the biological processes that precede or accompany Alzheimer’s disease, rather than focusing only on the disease’s most familiar molecular features. The study’s links to microglial immune activity and neuronal gene expression may guide further research into how inherited differences relate to brain changes.
The findings also matter for risk research. If estimation methods capture genetic contribution differently, estimates used to describe inherited susceptibility and develop prediction tools may need careful comparison. But a population-level association does not establish that a particular person will develop the disease, and the study does not show that its findings can yet improve clinical risk prediction.
The investigators highlighted five potential targets—RRM2B, SYK, KEAP1, CACNA1S and AXL—for further study. These are research leads, not treatments validated by this analysis. The report notes that prior experimental work on some targets was promising, while cited studies involving CACNA1S and AXL did not improve outcomes.
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From Heritability Estimates to Risk Loci
Alzheimer’s disease is the most common form of dementia. The study report says twin research has estimated that 60% to 80% of susceptibility may be heritable, while earlier genome-wide association studies had identified about 80 risk loci. Estimates based on common single-nucleotide polymorphisms had put their contribution to disease liability at about 5%. These figures refer to different ways of measuring inherited influence and should not be treated as interchangeable.
The new work expands the number of associated loci and examines biological pathways and cell types. Its analyses used clinical diagnoses or medical coding to define cases; some cohorts included unspecified dementia codes. The researchers applied fine-mapping, gene-based analyses and other methods to prioritize genes, then assessed genetic findings across ancestry groups.
Although the study included participants from European, African, East Asian, admixed American and South Asian ancestry groups, the effective sample was heavily weighted toward European ancestry. The authors reported that results for groups with smaller samples were less precise, a limitation for applying findings across populations.
“The study investigates whether existing methods underestimate the genetic contribution to Alzheimer’s disease.”
— The study authors, as described in the report
Limits of the Risk Estimates
The report does not specify a replacement percentage for the earlier estimate of common-variant contribution, nor does it establish that one heritability method should replace another. The result supports scrutiny of how estimates are calculated, but the size of any revision remains unclear from the reported material.
Some biological relationships are also unresolved. Neuronal expression associations weakened after adjustment for average differences across cell types, and it is not clear whether the observed neuronal changes contribute to Alzheimer’s or result from neurodegeneration. No individual microglial state reached statistical significance, even though inflammatory microglial states showed the strongest association.
Finally, the study’s drug-target analysis was not a clinical treatment test. It did not establish whether altering any highlighted gene would prevent or treat Alzheimer’s, and the ancestry imbalance limits the precision of comparisons for underrepresented groups.
Further Tests of Genes and Methods
The immediate next step is independent research to test the genetic associations, clarify how different estimation methods compare and examine findings in larger, more balanced ancestry cohorts. Researchers would also need to establish whether the implicated genes and cell processes play a causal role, rather than merely appearing alongside disease risk.
Any proposed treatment based on these results would require laboratory and clinical testing before its safety or effectiveness could be assessed in people. The study offers candidates and pathways for that work; it does not announce a new Alzheimer’s therapy or a change to current patient care.
Key Questions
What did the study find?
Researchers reported 127 Alzheimer’s-associated genetic loci, including 48 not previously identified in the analysis, and linked genetic signals to several biological pathways and cell types.
Does this mean Alzheimer’s is mostly genetic?
No. The study examines inherited susceptibility and methods for estimating it. Its reported findings do not provide a new definitive percentage of Alzheimer’s risk attributable to genes, and population-level heritability does not predict an individual’s outcome.
Were the proposed gene targets tested as treatments?
No. The researchers identified potential targets, including SYK and AXL, but did not test them as Alzheimer’s treatments in this study.
How representative were the genetic data?
The data included several ancestry groups, but about 91% of the effective sample was of European ancestry. The report says results in groups with smaller samples were less precise.
Source: news-medical.net
