Full Breakdown
Conflicting Findings on Clonal Hematopoiesis and Alzheimer’s Disease Risk
8/21/2026, 9:37:21 PM
Core Findings: Divergent Conclusions from Recent Studies
Two recent investigations have reached opposite conclusions about whether clonal hematopoiesis of indeterminate potential (CHIP) influences Alzheimer’s disease (AD).
- Siddhartha Jaiswal and colleagues (2023) reported that individuals with CHIP were 36 % less likely to develop Alzheimer’s dementia, citing Mendelian-randomization evidence that the same genetic variants that increase CHIP also decrease AD risk. Post-mortem analysis of eight octogenarian brains showed CHIP-derived mutations in up to 95 % of microglia, suggesting a protective role.
- Christopher A. Walsh’s team, using deeper sequencing of 190 AD brains and 121 controls, found significantly more CHIP mutations in AD specimens. The mutations clustered in microglia with a disease-associated (DAM) transcriptional profile marked by inflammation and proliferation, which the authors interpreted as a driver of neurodegeneration.
Both studies examined the same CHIP-related genes (primarily TET2 and DNMT3A) but arrived at opposite interpretations of the same biological phenomenon.
Background & Context
CHIP describes the expansion of blood-cell clones that carry somatic mutations in cancer-driver genes. By age 70, 10 %–30 % of people harbor detectable CHIP clones, most of which remain clinically silent. Historically, CHIP has been linked to higher risks of leukemia, atherosclerosis, stroke, chronic liver disease, and arthritis. The new focus is whether these mutant clones, which can cross the blood-brain barrier and become indistinguishable from resident microglia, affect AD pathology.
Conflicting Reports & Gaps
- Interpretation of mutation burden – Jaiswal argues that CHIP-derived microglia improve amyloid and tau clearance, whereas Walsh views the same DAM-state microglia as inflammatory contributors.
- Methodological differences – Jaiswal’s cohort-level approach captured clones comprising >=5 %–8 % of blood cells; Walsh’s ultra-deep sequencing detected clones as rare as <0.1 %, revealing a different risk pattern.
- Causality vs. consequence – Jaiswal contends inflammation in AD brains is a response to pathology; Walsh suggests the DAM state may be driven by CHIP mutations.
- Gene specificity – King emphasizes that TET2 and DNMT3A mutations may have opposite effects, a nuance not fully resolved in either study.
- Longitudinal evidence – Both studies are observational; prospective data linking CHIP status to incident AD are lacking.
Official Statements & Responses
- Siddhartha Jaiswal (Stanford) emphasized that “the cells need to get into the brain to exert their protective effect.”
- Christopher A. Walsh (Boston Children’s) described the mutant microglia as “the vast majority of the microglia that are in the DAM state are carrying these CHIP mutations.”
What’s Next: Trials and Predictions
- Anti-inflammatory agents that block interleukin-1? (e.g., canakinumab) have reduced cardiovascular events in CANTOS; Jaiswal predicts similar drugs will likely succeed for heart disease but not for neurodegeneration.
- Walsh proposes repurposing cancer drugs that target CHIP-related pathways for AD, noting potential limitation to early disease stages.
- Ongoing phase-2 trials of NLRP3 inflammasome inhibitors aim to clarify whether dampening microglial inflammation can modify AD progression.
The divergent interpretations underscore uncertainty: whether CHIP-derived immune cells are protective allies, harmful agitators, or simply bystanders in AD. Resolving this will require longitudinal cohorts, functional experiments, and gene-specific analyses.
