TheGenetics ofCentenarians:WhatMolecularBiologyKnowsAbout the 100-YearThreshold

Why do some people reach 100 in relative health, while others decline at 70?Partly lifestyle.Partly luck.But partly genetics.And science has begun to decode this portion with increasing precision.

Part 1.APOE —TheMostImportantGene forYourOldAge

TheAPOE gene encodes apolipoproteinE, which participates in lipid transport and neuroprotection.It comes in three main variants: ε2, ε3, ε4.

• APOE ε3: the most common variant (~78% of the population). 'Neutral' with respect to longevity risk.
• APOE ε2: rare (~8%).Associated with a reduced risk ofAlzheimer's disease and with higher representation among centenarians.A protective variant.
• APOE ε4: carriers of one copy have a 3–4 times higher risk ofAlzheimer's than average.Carriers of two copies (approximately 2% of the population) — 8–12 times higher.Among centenarians over 100, the frequency of ε4 is significantly lower than in the general population.

How to find it in your test:SNPs rs429358 and rs7412.Their combination determines theAPOE genotype.In 23andMe, the result is available under 'HealthPredispositions' (requires a separate consent step).

Part 2.FOXO3 —TheGeneFound inHawaiianCentenarians

In 2008, a research group led byBradleyWillcox published a study inPNAS of 213 men ofJapanese descent inHawaii who had lived to 95+.The key finding: a variant of theFOXO3 gene was significantly more common in centenarians than in the control group.

FOXO3 (ForkheadBoxO3) is a transcription factor that regulates several processes critical to longevity:

• Cellular autophagy: clearing cells of damaged organelles and protein aggregates.
• DNA repair: activating mechanisms that correctDNA damage.
• Antioxidant defence: regulating genes that neutralise reactive oxygen species.
• Apoptosis: controlled death of damaged cells rather than their malignant transformation.

Willcox's results were replicated in several independent cohorts —German,Danish,Italian,French.FOXO3 is one of the most reproducible genetic longevity factors identified to date.

How to find it in your test:SNP rs2802292.TheG allele is associated with the protective effect.Carriers of theGG genotype show the strongest longevity effect.

Part 3.CETP and theCholesterol ofCentenarians

The protein product of theCETP gene (CholesterylEsterTransferProtein) transfers cholesterol esters between lipoprotein particles.Its activity affects the ratio ofHDL ('good' cholesterol) toLDL ('bad' cholesterol).

A study ofNewYorkAshkenaziJewish centenarians (Barzilai et al.,JAMA, 2003): among centenarians over 95, variants ofCETP that reduce enzyme activity were significantly more common.This resulted in anomalously highHDL levels — in some cases twice the normal range — and in largeLDL particles less prone to atherogenesis.

Part 4.Telomeres:MolecularClocks orSimplyMarkers?

Telomeres are repetitiveDNA sequences (TTAGGG in humans) at the ends of chromosomes.With each cell division they shorten slightly.When telomeres become too short, the cell stops dividing (senescence) or dies.This phenomenon was described bySoviet-American biologistAlexeiOlovnikov in 1971, andElizabethBlackburn,CarolGreider, andJackSzostak received theNobelPrize in 2009 for their research on telomeres and telomerase.

What we know reliably:

• Telomere length declines with age in everyone.
• Chronic stress, obesity, smoking, and a sedentary lifestyle accelerate telomere shortening.
• Physical activity, meditation, and omega-3 fatty acids are associated with slowed shortening.
• Longer telomeres correlate with longevity — but non-linearly: excessively long telomeres are associated with an elevated risk of certain cancers.

What remains debated:

• Are telomeres a cause of ageing or a marker of it?Most researchers lean toward short telomeres being an indicator of cellular stress, not its primary cause.
• Commercial telomere length tests: their reproducibility and clinical significance remain contested.Measuring telomere length in white blood cells (the standard method) does not necessarily reflect telomere length in other tissues.

Part 5.EpigeneticClocks:TheMostAccurateTool forMeasuringBiologicalAge

The epigenetic clocks developed by biostatisticianSteveHorvath in 2013 (GenomeBiology) measure the pattern ofDNA methylation — chemical tags on nucleotides that regulate gene activity.These tags change with age in a predictable way.

Horvath's clock covers 353CpG sites (methylation points) and predicts biological age from a sample of any tissue with an accuracy of approximately 3–5 years.Later clocks —GrimAge (2019) andDunedinPACE (2022) — more accurately predict not just biological age but the pace of ageing and mortality risk.

Summary:WhatCanActuallyBeChecked inYourDNATest

If you have results from a consumerDNA test (23andMe,AncestryDNA), here is what is worth checking:

• APOE: rs429358 + rs7412.DeterminesAlzheimer's risk and cardiovascular profile.
• FOXO3: rs2802292.TheG allele is protective in the context of longevity.
• CETP: rs5882.TheI405V variant affectsCETP activity andHDL level.
• MTOR andSIRT1/SIRT3: genes regulating cellular ageing and autophagy.Less specific thanFOXO3 andAPOE, but relevant in the context of nutrigenomics.

For those who want to go further: commercial epigenetic tests (TruAge,ElysiumIndex,MyDNAge) provide a biological age estimate fromDNA methylation in a saliva sample.