What you carry at this position in your DNA and what research says about it.
Alzheimer's Disease Risk: 8/10 evidence, 21 publications.
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Sample genotype (not yours): A/A
Increased Risk of Late-Onset Alzheimer's
Two copies of the A allele are linked to a slightly higher risk of late-onset Alzheimer's disease. This genetic profile is also associated with increased amyloid plaque accumulation in the brain.
What this genotype means: ~1.18x higher risk of late-onset Alzheimer's; Increased accumulation of brain amyloid plaques; Higher risk of cerebral amyloid angiopathy.
Sample genotype (not yours): A/G
One copy of the A allele is associated with a slightly elevated risk of late-onset Alzheimer's disease. This genotype may also lead to higher amyloid plaque accumulation in brain blood vessels.
Sample genotype (not yours): G/G
Typical Risk of Late-Onset Alzheimer's
Two copies of the common G allele are associated with typical risk of late-onset Alzheimer's disease. This genotype supports standard clearance of amyloid-beta proteins from the brain.
What this genotype means: Typical risk of late-onset Alzheimer's; Standard clearance of amyloid-beta proteins; Typical risk of cerebral amyloid angiopathy.
Gene function and biological role
Gene Function: The CR1 gene encodes complement receptor 1, a membrane glycoprotein found on red blood cells and immune cells [1]. This receptor plays a critical role in the immune system's complement cascade, which helps clear foreign pathogens and cellular debris [1]. In the brain, complement receptor 1 is heavily involved in the clearance of amyloid-beta peptides, preventing them from accumulating into toxic plaques [2]. When the complement system functions suboptimally, amyloid-beta can build up, driving neurodegeneration and cognitive decline [2]. Beyond Alzheimer's, CR1 is also studied for its role in other vascular and inflammatory conditions of the central nervous system [3].
Variant Impact: The rs6656401 variant is an intronic change located within the CR1 gene on chromosome 1. This genetic variation is strongly associated with late-onset Alzheimer's disease risk across multiple populations [4]. Research indicates that the risk-associated allele alters the expression of complement receptor 1 isoforms on the surface of red blood cells [1]. This alteration reduces the efficiency of amyloid-beta clearance from the brain and bloodstream [1]. Consequently, carriers of the risk allele tend to accumulate higher levels of amyloid plaques in brain tissue and blood vessels [2].
Key Insight: The CR1 gene helps red blood cells act like a vacuum, capturing toxic amyloid proteins in the bloodstream to clear them from the brain.
Location: CR1. Chromosome 1 · 1q32.2 · 207.5 Mb
Estimated prevalence by population
Global 2.2%; European 3.5%; African 0.1%; East Asian 0.1%; South Asian 0.6%; Americas 1.6%; Ashkenazi 3.3%; Finnish 3.3%; Middle Eastern 3.1%; Amish 4.0%.
Estimated AA genotype frequency.
Global 21.7%; European 30.6%; African 6.5%; East Asian 6.7%; South Asian 14.4%; Americas 22.3%; Ashkenazi 29.9%; Finnish 29.9%; Middle Eastern 29.1%; Amish 32.1%.
Estimated AG genotype frequency.
Global 76.1%; European 65.9%; African 93.4%; East Asian 93.2%; South Asian 85.0%; Americas 76.0%; Ashkenazi 66.8%; Finnish 66.7%; Middle Eastern 67.7%; Amish 63.8%.
Estimated GG genotype frequency.
Showing effects for A/A genotype
Neurology & Mental Health
Neurodegenerative Diseases
Alzheimer's Disease. Evidence: 8/10. Source: PMID 19734903. ~1.18x Increased Risk.
Amyloid Deposition. Evidence: 3/10. Source: PMID 22262751. Increased Accumulation.
Amyloid Angiopathy. Evidence: 3/10. Source: PMID 22262751. ~1.6x Increased Risk.
Neurodevelopmental Traits
Brain Structure. Evidence: 3/10. Source: PMID 21726919. Altered Brain Volume.
Mood Disorders
Depression. Evidence: 3/10. Source: PMID 22244847. Increased Risk.
Showing effects for A/G genotype
Showing effects for G/G genotype
Alzheimer's Disease. Evidence: 8/10. Source: PMID 19734903. Typical Risk.
Amyloid Deposition. Evidence: 3/10. Source: PMID 22262751. Typical Clearance.
Amyloid Angiopathy. Evidence: 3/10. Source: PMID 22262751. Typical Risk.
Brain Structure. Evidence: 3/10. Source: PMID 21726919. Typical Brain Volume.
Depression. Evidence: 3/10. Source: PMID 22244847. Typical Risk.
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Late-onset Alzheimer's disease risk is moderately elevated in individuals with this genetic profile [1]. The complement receptor 1 protein, encoded by the CR1 gene, plays a vital role in clearing amyloid-beta peptides from brain tissue [2]. Having two copies of the A allele is associated with reduced complement receptor efficiency, leading to higher amyloid plaque burden [2]. This genotype also increases the risk and severity of cerebral amyloid angiopathy, a condition where amyloid builds up in the walls of brain blood vessels [3]. Furthermore, neuroimaging studies show that this variant correlates with structural alterations in the entorhinal cortex and other brain regions involved in memory [4]. Some research also suggests a potential link between this genetic variation and an increased susceptibility to depression [5].
~1.18x higher risk of late-onset Alzheimer's; Increased accumulation of brain amyloid plaques; Higher risk of cerebral amyloid angiopathy.
Sample genotype: AG (Heterozygous)
A single copy of the A allele is sufficient to moderately increase the risk of late-onset Alzheimer's disease [1]. The CR1 gene is responsible for producing complement receptor 1, which helps clear toxic amyloid-beta proteins from the brain [2]. With this genotype, the clearance mechanism is less efficient, which can lead to a higher density of amyloid plaques [2]. This genetic variation also elevates the risk of cerebral amyloid angiopathy, which can weaken blood vessels in the brain [3]. Brain imaging studies have shown that carriers of this allele exhibit differences in entorhinal cortex volume, a region critical for memory formation [4]. Additionally, some studies have identified a correlation between this variant and an increased risk of depression [5].
Sample genotype: GG (Homozygous)
Standard risk of late-onset Alzheimer's disease is typical for individuals with this genetic profile [1]. The complement receptor 1 protein functions normally, facilitating the efficient clearance of amyloid-beta peptides from the brain and bloodstream [2]. This efficient clearance helps prevent the excessive accumulation of toxic amyloid plaques in brain tissue [2]. Consequently, this genotype is associated with a lower risk of cerebral amyloid angiopathy compared to risk-allele carriers [3]. Neuroimaging studies indicate typical brain structure and volume in memory-related regions like the entorhinal cortex [4]. There is also no elevated risk of depression associated with this genetic variant [5].
Typical risk of late-onset Alzheimer's; Standard clearance of amyloid-beta proteins; Typical risk of cerebral amyloid angiopathy.
Variants with shared genetic architecture
rs3818361 · CR1 Gene · Chr 1 · Alzheimer's Risk
rs11218343 · SORL1 Gene · Chr 11 · Alzheimer's Risk
rs9331896 · CLU Gene · Chr 8 · Alzheimer's Disease Risk
Genetic variation at CR1 increases risk of cerebral amyloid angiopathy.
Alzheimer's disease risk factor complement receptor 1 is associated with depression.
CR1 genotype is associated with entorhinal cortex volume in young healthy adults.
Content updated August 2026.
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