PER2 rs1149498: Understanding Your Circadian Clock Variant
The rs1149498 variant is a common genetic marker located within the PER2 gene, which plays a central role in maintaining the human circadian rhythm. Research suggests this variant may be associated with individual differences in diurnal preference, specifically relating to eveningness and the timing of sleep-wake cycles.
What each genotype means
Typical circadian phase
This genotype represents the most common configuration for this variant in many populations. Research into this PER2 variant suggests it may play a role in modulating diurnal preference, though the evidence linking this specific site to sleep timing remains limited and inconsistent across different studies. Your sleep patterns are likely influenced by a complex interplay of many genetic factors and environmental influences rather than this single variant.
This is the most common genotype, carried by the majority of individuals in European populations.
Potential circadian modulation
Carrying one copy of the minor allele may be associated with subtle shifts in diurnal preference, such as a tendency toward eveningness or delayed sleep phase. However, findings regarding this variant are mixed, and it is not a definitive predictor of sleep behavior. You should view this as a minor contributor to your overall chronotype rather than a diagnostic indicator.
This genotype is carried by roughly 1 in 6 to 1 in 8 people of European ancestry, and is less common in other global populations.
Possible eveningness preference
Individuals with this genotype may be statistically more likely to exhibit an evening-oriented chronotype or a slight delay in their natural sleep-wake cycle. Because the evidence for this variant's impact is limited and results have been inconsistent across different research cohorts, this genotype should not be used to infer specific sleep disorders. Lifestyle factors and other genetic markers are likely more significant in determining your personal sleep timing.
This is the least common genotype, found in a small minority of individuals of European ancestry.
What is rs1149498 and Where is it Located?
The variant rs1149498 is a single-nucleotide polymorphism (SNP) situated within the PER2 gene. In genetics, a SNP represents a variation at a single position in the DNA sequence among individuals. The PER2 gene, or Period Circadian Regulator 2, is located on human chromosome 1. This specific variant is categorized as a tagging variant, meaning it is often used by researchers to track or 'tag' a specific region of the genome that may be inherited together. Because it is located within a gene critical for biological timing, scientists study it to understand how subtle changes in our DNA sequence might influence the complex, internal mechanisms that govern our daily sleep and wake patterns.
The Role of the PER2 Gene
The PER2 gene is a fundamental component of the molecular machinery that drives the human circadian clock. This clock is an internal system that synchronizes our physiological processes—such as hormone release, body temperature, and sleep-wake cycles—with the 24-hour light-dark cycle of the environment. PER2 functions as a transcriptional repressor, meaning it helps turn off the activity of other clock-related genes. By forming a negative feedback loop with other proteins like CLOCK and BMAL1, PER2 ensures that the expression of clock-controlled genes oscillates in a rhythmic, predictable manner. Disruptions or variations in this gene can potentially alter the period or 'tau' of these rhythms, which is the length of time it takes for one complete cycle to occur.
Research Associations and Evidence Strength
Current research into rs1149498 and its link to circadian traits is considered to have limited evidence strength. While the PER2 gene is well-established as a regulator of sleep timing, the specific functional impact of the rs1149498 variant remains a subject of ongoing investigation. Some studies have explored its association with 'eveningness,' a preference for later sleep and wake times, and diurnal phase delay. However, it is important to note that circadian traits are polygenic, meaning they are influenced by many different genes, as well as environmental and social factors. Because of this complexity, the association between this single SNP and a person's sleep preference is not definitive. Findings can vary significantly between different study populations, and more large-scale research is required to fully understand the clinical or behavioral significance of this specific variant.
Population Frequency
The rs1149498 variant is relatively common, with a minor allele frequency of approximately 10-15% in European populations. Frequency data can vary across different global ancestries, and it is common for genetic variants to show different prevalence rates depending on the ancestral background of the population being studied. Understanding these frequencies is a key part of genomic research, as it helps scientists determine whether a variant is rare or common within a specific group. Because this variant is found in a significant portion of the population, it is considered a common genetic polymorphism rather than a rare mutation.
What You Can and Cannot Do With This Information
It is important to approach genetic information about circadian variants with a clear understanding of its limitations. You cannot use this information to diagnose a sleep disorder or to predict your exact sleep schedule, as your chronotype is shaped by a combination of genetics, age, lifestyle, and environmental light exposure. This information is for educational purposes only and should not be used to make medical decisions. If you are experiencing persistent sleep difficulties, such as extreme difficulty falling asleep or waking up, you should consult with a healthcare professional or a sleep specialist. They can provide a clinical evaluation that considers your full medical history, which is far more informative than any single genetic marker.
How common is this variant?
The minor allele frequency for rs1149498 is approximately 10-15% in European populations, making it a common genetic variant.
Frequently asked questions
Does having a specific PER2 genotype mean I have a sleep disorder?
No. Genetic variants like rs1149498 are associated with natural variations in sleep preference, not clinical sleep disorders. A diagnosis of a sleep disorder requires a professional evaluation by a doctor.
Can I change my sleep habits if I have this variant?
Yes. Circadian rhythms are highly adaptable. Lifestyle changes, such as consistent light exposure and sleep hygiene, often have a much larger impact on your sleep timing than any single genetic variant.
Is this variant the only thing that determines if I am a night owl?
No. Your sleep preference is influenced by many genes, your age, and your environment. No single SNP can fully explain or predict your personal chronotype.
Should I take supplements based on my PER2 genotype?
You should never start or change any supplement or medication regimen based on genetic test results without first consulting your doctor or a pharmacist. They can provide guidance based on your overall health.
Sources & further reading
Educational information only, last refreshed 9/24/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Pathogenic missense variant (Ser662Gly) in PER2 that impairs casein kinase phosphorylation, causing familial advanced sleep phase syndrome (FASPS-1).
This intronic variant in the PER2 gene is associated with individual differences in circadian rhythm, sleep timing, and chronotype.
Variant in the circadian regulator PER2 associated with circadian rhythm phase, chronotype, and timing of habitual sleep.
This variant is associated with familial advanced sleep phase syndrome, affecting the timing of the sleep-wake cycle.
A mutation in the PER2 gene associated with familial advanced sleep phase syndrome, leading to an earlier sleep-wake cycle.
An intronic single-nucleotide variant in the core clock gene PER2 recently identified in familial delayed sleep phase syndrome and evening chronotypes.