The Genetics of Centenarians: What Molecular Biology Knows About the 100-Year Threshold

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 — The Most Important Gene for Your Old Age

The APOE gene encodes apolipoprotein E, 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 of Alzheimer's disease and with higher representation among centenarians. A protective variant.
• APOE ε4: carriers of one copy have a 3–4 times higher risk of Alzheimer'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 the APOE genotype. In 23andMe, the result is available under 'Health Predispositions' (requires a separate consent step).

Part 2. FOXO3 — The Gene Found in Hawaiian Centenarians

In 2008, a research group led by Bradley Willcox published a study in PNAS of 213 men of Japanese descent in Hawaii who had lived to 95+. The key finding: a variant of the FOXO3 gene was significantly more common in centenarians than in the control group.

FOXO3 (Forkhead Box O3) 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 correct DNA 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. The G allele is associated with the protective effect. Carriers of the GG genotype show the strongest longevity effect.

Part 3. CETP and the Cholesterol of Centenarians

The protein product of the CETP gene (Cholesteryl Ester Transfer Protein) transfers cholesterol esters between lipoprotein particles. Its activity affects the ratio of HDL ('good' cholesterol) to LDL ('bad' cholesterol).

A study of New York Ashkenazi Jewish centenarians (Barzilai et al., JAMA, 2003): among centenarians over 95, variants of CETP that reduce enzyme activity were significantly more common. This resulted in anomalously high HDL levels — in some cases twice the normal range — and in large LDL particles less prone to atherogenesis.

Part 4. Telomeres: Molecular Clocks or Simply Markers?

Telomeres are repetitive DNA 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 by Soviet-American biologist Alexei Olovnikov in 1971, and Elizabeth Blackburn, Carol Greider, and Jack Szostak received the Nobel Prize 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. Epigenetic Clocks: The Most Accurate Tool for Measuring Biological Age

The epigenetic clocks developed by biostatistician Steve Horvath in 2013 (Genome Biology) measure the pattern of DNA methylation — chemical tags on nucleotides that regulate gene activity. These tags change with age in a predictable way.

Horvath's clock covers 353 CpG 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) and DunedinPACE (2022) — more accurately predict not just biological age but the pace of ageing and mortality risk.

Summary: What Can Actually Be Checked in Your DNA Test

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

• APOE: rs429358 + rs7412. Determines Alzheimer's risk and cardiovascular profile.
• FOXO3: rs2802292. The G allele is protective in the context of longevity.
• CETP: rs5882. The I405V variant affects CETP activity and HDL level.
• MTOR and SIRT1/SIRT3: genes regulating cellular ageing and autophagy. Less specific than FOXO3 and APOE, but relevant in the context of nutrigenomics.

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