CRY1 rs4964515: What Your Genotype Means
The rs4964515 variant is a single nucleotide polymorphism located within the CRY1 gene, which plays a central role in the human circadian clock. Research suggests this variant is associated with variations in sleep-wake timing and subjective sleep quality.
What each genotype means
Typical sleep-wake timing
This genotype represents the common version of the CRY1 variant. Research suggests this is the baseline state for circadian regulation in most individuals, without the specific associations linked to the minor allele.
This is the most common genotype observed in most global populations.
Potential sleep timing variation
Carriers of this genotype possess one copy of the minor allele, which has been associated in some studies with variations in sleep-wake timing and subjective reports of poor sleep quality. Because this is a complex trait influenced by many genes and environmental factors, this genotype does not guarantee a specific sleep pattern or disorder.
This genotype is found in approximately 20-30% of individuals in European and East Asian populations.
Increased sleep timing variation
Individuals with this genotype carry two copies of the minor allele, which is associated with a higher likelihood of reporting late sleep-wake timing or fragmented sleep. These associations are based on population-level data and may not reflect an individual's personal experience, as sleep behavior is highly multifactorial.
This genotype is less common than the heterozygous state, appearing in a smaller subset of the population based on the reported minor allele frequency.
Understanding the CRY1 Gene
The CRY1 gene encodes the Cryptochrome Circadian Regulator 1 protein, a critical component of the molecular machinery that drives our internal biological clock. This protein functions as a transcriptional repressor, meaning it helps turn off the expression of other clock genes in a rhythmic, 24-hour feedback loop. By interacting with other core clock proteins like CLOCK and BMAL1, CRY1 helps synchronize our physiological processes—such as hormone release, body temperature, and sleep-wake cycles—with the external environment. Because of its central role in maintaining the timing of these rhythms, variations in the CRY1 gene are frequently studied in the context of sleep disorders and circadian rhythm disturbances. When the function of this protein is altered, it can potentially shift the timing of when an individual feels alert or sleepy, a phenomenon often referred to as chronotype.
What is the rs4964515 Variant?
The rs4964515 variant is a specific genetic change, or single nucleotide polymorphism (SNP), situated within the CRY1 gene region. In genetics, a SNP represents a variation at a single position in the DNA sequence among individuals. While many SNPs have no observable effect on health or behavior, researchers investigate them to see if they correlate with specific traits. In the case of rs4964515, scientists have looked at whether the presence of different alleles at this location influences how the circadian clock functions. Unlike rare, highly penetrant mutations that might cause severe, clinically diagnosed sleep disorders, common variants like rs4964515 are typically studied for their subtle, cumulative effects on sleep timing and quality across the general population. It is important to distinguish this common variant from rare, pathogenic mutations in CRY1 that have been linked to familial delayed sleep phase disorder.
Research and Evidence Strength
The evidence linking rs4964515 to sleep traits is considered moderate. Large-scale genetic association studies, such as those utilizing data from the UK Biobank, have examined how variants in circadian genes influence sleep timing and duration. While some studies have identified statistical associations between CRY1 variants and sleep-wake timing, the effect sizes observed in the general population are often quite small—sometimes amounting to only a few minutes of difference in sleep midpoint. It is crucial to note that sleep is a complex trait influenced by a vast array of genetic, environmental, and lifestyle factors. Therefore, while rs4964515 may contribute to the biological predisposition for one's chronotype, it is not a sole determinant of sleep quality or timing. Current research continues to refine our understanding of how these genetic signals interact with the environment to shape human sleep behavior.
Interpreting Your Information
If you are curious about your genetic data, it is important to understand what this information can and cannot tell you. Genetic variants like rs4964515 provide a glimpse into the biological predispositions that might influence your natural sleep-wake preferences, but they do not constitute a medical diagnosis. Sleep patterns are highly plastic and can be significantly modified by habits, light exposure, and daily schedules. You cannot use this information to diagnose a sleep disorder or to predict your exact sleep behavior with certainty. If you are experiencing persistent sleep difficulties, such as chronic insomnia or extreme difficulty waking up, these are clinical concerns that should be addressed by a healthcare professional. A doctor or sleep specialist can provide a comprehensive evaluation that considers your medical history, lifestyle, and symptoms, which is far more informative than any single genetic marker.
How common is this variant?
The minor allele frequency for rs4964515 is approximately 0.20 to 0.30 in European and East Asian populations, making it a relatively common genetic variant.
Frequently asked questions
Does having a specific CRY1 genotype mean I have a sleep disorder?
No. Genetic variants like rs4964515 are associated with natural variations in sleep timing, not necessarily with clinical sleep disorders. A diagnosis of a sleep disorder requires a professional evaluation by a healthcare provider.
Can I change my sleep habits if I have this variant?
Yes. Sleep patterns are influenced by both genetics and environment. Lifestyle changes, such as consistent sleep schedules and light management, can often help individuals manage their sleep-wake timing regardless of their genetic background.
Is rs4964515 the same as the CRY1 mutation that causes delayed sleep phase disorder?
No. The rare, gain-of-function mutation (c.1657+3A>C) linked to familial delayed sleep phase disorder is distinct from the common SNP rs4964515. They are different genetic markers with different levels of impact.
Should I take supplements based on my CRY1 genotype?
You should never start or change a supplement regimen based on genetic data without consulting a doctor or pharmacist. They can help determine if any intervention is safe and appropriate for your specific health needs.
Sources & further reading
Educational information only, last refreshed 9/30/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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This intronic variant in the CRY1 gene is associated with delayed sleep-wake phase disorder (DSWPD) and has been linked to variations in glycemic parameters and insulin resistance.
This splice donor mutation (c.1657+1G>A) causes exon 11 skipping, leading to an overactive repressor complex and familial delayed sleep phase disorder.
Variant in the CRY1 gene, which encodes a core component of the circadian clock, associated with sleep timing and delayed sleep phase.
Dominant splice-site mutation (c.1657+3A>C) in CRY1, resulting in skipping of exon 11 and associated with delayed sleep-wake phase disorder (DSWPD).
Variant in the CRY1 locus associated with sleep timing and circadian rhythm traits; distinct from rare high-penetrance mutations.
This SNP is located in the CRY1 gene, which encodes a core circadian clock protein involved in regulating sleep-wake cycles.