What you carry at this position in your DNA and what research says about it.
Alzheimer Disease Risk: 10/10 evidence, 25 publications.
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Sample genotype (not yours): C/C
Typical Alzheimer's Risk
Carrying two copies of the common C allele represents the standard genetic baseline. This genotype is not associated with the elevated risk of Alzheimer's disease or early cognitive decline.
What this genotype means: Typical risk of late-onset dementia; Typical age of cognitive aging.
Sample genotype (not yours): C/T
~2.5x Higher Alzheimer's Risk
Carrying one copy of the rare T allele is linked to a significantly increased risk of developing late-onset Alzheimer's disease. It may also lead to an earlier age of symptom onset.
What this genotype means: Significantly increased risk of late-onset Alzheimer's; Potential for earlier onset of cognitive symptoms.
Sample genotype (not yours): T/T
Highly Increased Alzheimer's Risk
Carrying two copies of the rare T allele is extremely uncommon and is associated with a highly elevated risk of Alzheimer's disease and accelerated neurodegeneration.
What this genotype means: Highly elevated risk of late-onset Alzheimer's; Accelerated rate of cognitive decline.
Gene function and biological role
Gene Function: TREM2 encodes a receptor primarily found on microglia, the resident immune cells of the brain [1]. This receptor plays a pivotal role in regulating microglial activity, survival, and inflammatory responses [1]. Under normal conditions, TREM2 helps microglia recognize and clear cellular debris, amyloid-beta plaques, and damaged neurons [2]. When TREM2 function is compromised, microglia are unable to properly envelop toxic amyloid plaques, leading to accelerated brain pathology [1]. Consequently, genetic variations in TREM2 are among the strongest known risk factors for late-onset Alzheimer's disease [2].
Variant Impact: The rs75932628 variant represents a missense mutation in exon 2 of the TREM2 gene, resulting in an arginine-to-histidine substitution at position 47 of the protein [2]. This specific amino acid change alters the extracellular ligand-binding domain of the receptor, significantly reducing its affinity for amyloid-beta and other ligands [1]. As a result, microglia carrying this variant exhibit a partial loss of function, failing to cluster effectively around amyloid plaques or transition into a protective, disease-associated state [1]. This impairment leads to reduced clearance of toxic proteins and increased neurodegeneration [1].
Key Insight: The TREM2 R47H variant is one of the strongest genetic risk factors for Alzheimer's disease, carrying an effect size comparable to the well-known APOE e4 gene.
Location: TREM2. Chromosome 6 · 6p21.1 · 41.2 Mb
Estimated prevalence by population
Global 99.6%; European 99.6%; African 99.9%; East Asian 100.0%; South Asian 99.3%; Americas 99.0%; Ashkenazi 97.4%; Finnish 99.9%; Middle Eastern 98.6%; Amish 100.0%.
Estimated CC genotype frequency.
Global 0.4%; European 0.4%; African 0.1%; East Asian 0.0%; South Asian 0.7%; Americas 1.0%; Ashkenazi 2.6%; Finnish 0.1%; Middle Eastern 1.4%; Amish 0.0%.
Estimated CT genotype frequency.
Global < 0.1%; European < 0.1%; African < 0.1%; East Asian 0.0%; South Asian < 0.1%; Americas < 0.1%; Ashkenazi < 0.1%; Finnish < 0.1%; Middle Eastern < 0.1%; Amish 0.0%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Neurology & Mental Health
Neurodegenerative Diseases
Alzheimer's Disease. Evidence: 10/10. Source: PMID 23150908. Typical Risk.
Age of Dementia Onset. Evidence: 8/10. Source: PMID 33637690. Typical Age.
Cognitive Performance
Cognitive Decline. Evidence: 6/10. Source: PMID 23150908. Typical Decline.
Immunity & Inflammation
Inflammatory & Circulating Protein Markers
Soluble TREM2 Levels. Evidence: 8/10. Source: PMID 38172904. Typical Levels.
Showing effects for C/T genotype
Alzheimer's Disease. Evidence: 10/10. Source: PMID 23150908. ~2.45x Increased Risk.
Age of Dementia Onset. Evidence: 8/10. Source: PMID 33637690. Earlier Onset.
Cognitive Decline. Evidence: 6/10. Source: PMID 23150908. Accelerated Decline.
Soluble TREM2 Levels. Evidence: 8/10. Source: PMID 38172904. Altered Levels.
Showing effects for T/T genotype
Alzheimer's Disease. Evidence: 10/10. Source: PMID 23150908. Highly Increased Risk.
Age of Dementia Onset. Evidence: 8/10. Source: PMID 33637690. Significantly Earlier.
Cognitive Decline. Evidence: 6/10. Source: PMID 23150908. Highly Accelerated.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Carrying two copies of the common C allele is the standard genetic baseline for the majority of the global population [1]. Individuals with this genotype produce a fully functional TREM2 receptor, allowing microglia to efficiently clear cellular waste and protect brain tissue [2]. Research shows that having the typical C/C genotype does not elevate the risk of late-onset Alzheimer's disease [1]. Furthermore, these individuals do not experience the accelerated cognitive decline or earlier age of dementia onset associated with the rare T variant [3]. Brain imaging and biomarker studies indicate typical levels of soluble TREM2 in cerebrospinal fluid [4]. Overall, this genotype provides a standard, non-elevated risk profile for neurodegenerative conditions [1].
Typical risk of late-onset dementia; Typical age of cognitive aging.
Sample genotype: CT (Heterozygous)
Having one copy of the rare T allele (the R47H variant) is a well-established genetic risk factor for Alzheimer's disease [1]. Large-scale genetic studies have consistently demonstrated that carriers of this variant face a two- to four-fold increase in their risk of developing late-onset dementia [1]. This risk is comparable in magnitude to carrying the well-known APOE e4 risk allele [2]. The mutation causes microglia to lose their ability to properly clear amyloid plaques, leading to increased neurodegeneration [2]. Additionally, carriers of this genotype may experience an earlier age of disease onset by several years compared to non-carriers [3]. Some studies suggest that the presence of an APOE e4 allele may further interact with this variant to influence disease progression [4].
Significantly increased risk of late-onset Alzheimer's; Potential for earlier onset of cognitive symptoms.
Sample genotype: TT (Homozygous)
Carrying two copies of the rare T allele is exceptionally rare, given that the variant occurs in less than 1% of the population [1]. This homozygous genotype is expected to cause a profound loss of TREM2 receptor function in the brain's immune cells [2]. Without functional TREM2, microglia cannot effectively clear toxic amyloid-beta plaques or support neuronal survival, leading to aggressive neurodegeneration [2]. Clinical and genetic data associate this variant with a significantly higher risk of late-onset Alzheimer's disease [1]. It is also linked to a substantially earlier age of dementia onset and rapid cognitive decline [3]. While other rare homozygous TREM2 mutations can cause severe bone and brain syndromes, the R47H variant is primarily studied for its strong impact on late-onset dementia [1].
Highly elevated risk of late-onset Alzheimer's; Accelerated rate of cognitive decline.
Variants with shared genetic architecture
rs28834970 · PTK2B Gene · Chr 8 · Alzheimer's Disease Risk
rs3865444 · CD33 Gene · Chr 19 · Alzheimer's Disease Risk
rs2718058 · NME8 Gene · Chr 7 · Alzheimer's Disease Risk
Variant of TREM2 associated with the risk of Alzheimer's disease.
APOE ε4 is also required in TREM2 R47H variant carriers for Alzheimer's disease to develop.
Content updated August 2026.
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