The 12 Hallmarks of Aging, and Exercise Hits Seven
In 2013 a team listed nine things that go wrong as the body ages. Ten years later they added three more. The twelve feed each other.
18 min read
A comprehensive guide to aging science from multiple perspectives.
There's no required reading order. Start wherever your curiosity takes you.
Every article cites sources. Where the science is uncertain, we say so.
This guide is continuously updated as new research emerges and as we add more curated articles to each lens.
Before we talk about what to do, understand what's actually happening in your body. The hallmarks of aging provide the foundation for everything else.
In 2013 a team listed nine things that go wrong as the body ages. Ten years later they added three more. The twelve feed each other.
Everyone comes to aging from a different place. Each lens offers a different way into the same subject.
For those who want to understand the mechanisms
In 2013 a team listed nine things that go wrong as the body ages. Ten years later they added three more. The twelve feed each other.
Several thousand older Poles were studied. Among those aging well, 2.9% of the least inflamed died within three years. Of the most inflamed, 25.3% did.
A fasting glucose of 99 comes back normal. So does 80, and the risk is not the same. The normal range is drawn around 95 out of 100 people the lab tested.
In deep sleep, the space between your brain cells opens up by about 60%. Fluid runs through and washes out the day's waste, including Alzheimer's proteins.
Oxygen crosses into the blood there, the heart moves it, and the muscles burn it. Trained athletes rest at 40 to 50 beats a minute, against 70 to 80.
In a 31-person trial, 47 percent of patients on dasatinib plus quercetin had less liver scarring, against 7 percent on placebo. Authors want a larger trial.
Median lifespan rose from 742 to 834 days, about 12 percent, when female mice started semaglutide at 20 months. No human lifespan data exist.
Their signal, PD-L2, rises in human blood with age. Old mice bred without it kept fewer of these cells and handled sugar better. No person has been treated.
TAME has no registration and has never begun. Its closest randomized test followed 3,234 adults without diabetes for 21 years and found no survival gain.
93 people, average age 60, joined a juggling study. Only some learned it, and their brains grew. Three months after they stopped, their brains went back.
Six leading tests were run twice on one DNA sample. The widest gap was 4.5 to 8.6 years. No intervention has ever moved a clock that far.
PEARL pre-registered visceral fat as its primary outcome. It came back at p = 0.942. Nearly everything quoted as a PEARL finding came from elsewhere in the paper.
The bone and lipid changes are measured and sharp. The epigenetic clock claim is not: no study has run one on the same women before and after menopause.
Canagliflozin added 14 percent to median lifespan in male mice. Females got three times more drug in their blood and no benefit at all.
Mice on a low-methionine diet eat freely, sometimes more than normal, and still live longer. The closest thing to caloric restriction without the calorie counting.
Neurons survive by recycling. When that cleanup fails, Alzheimer's accelerates. Restoring it may slow disease in ways amyloid drugs cannot.
Median mouse lifespan rose 9 to 26 percent even when dosing began at 20 months. Whether a healthy person should take it off-label is unanswered.
Clearing them from mice extended median lifespan by 17 to 35 percent. The human trials are tiny: one 2019 senolytic study had 14 people.
Zone 2 and resistance training are the only interventions with large, replicated effects. The supplement shelf is a different story.
We added two decades to human life last century. About ten of those years are spent sick. The gap between living longer and living well is the real longevity problem.
The SELECT trial cut major heart events by 20 percent in adults without diabetes. About two thirds of the lost weight returns within 12 months of stopping.
For those who want actionable guidance
In the places where people live longest, about 95% of the calories come from plants. Beans are a staple. Meat is mostly for special occasions.
The CALERIE trial asked adults to cut a quarter of their calories for two years. They managed about 12 percent. The slowdown showed up anyway.
The science behind cardiorespiratory fitness as the strongest predictor of lifespan - and why the humble 'easy run' might matter more than you think.
For those focused on cognitive health and psychology
In 2004 researchers measured telomere length in mothers, some caring for a sick child. The gap matched how stressed they said they felt.
Over 1,200 older people at risk of dementia were split in two. Half got exercise, diet, brain training, company and heart checks. Their thinking improved 25% more.
Social isolation increases mortality risk by 29-50%, rivaling smoking. How relationships affect inflammation, brain health, and biological aging.
A 2026 Nature Medicine study mapped 73 environmental and social factors against brain scans of 18,701 people in 34 countries.
Hearing aids slowed cognitive decline by 48% in older adults already at higher risk of it. Hearing loss is the biggest dementia risk you can change.
For those interested in physical optimization
About 35 percent of American adults have it, and the share climbs with age. You can be thin and still have it: weight alone does not decide.
A 2026 mouse study in Aging Cell separated the two directly. In worms, flies and mice, turning insulin signaling down extends life, not up.
Researchers studied 186 pairs of identical twins. The twin who got more sun looked older. Same genes, same age, different skin.
Cortisol is the most vilified hormone in wellness. It's also the reason you wake up, survive surgery, and think under pressure.
A 1968 study kept young men in bed for three weeks. They lost 27% of their VO2 Max. Three weeks did more to their fitness than the next thirty years.
For those exploring evidence-based supplementation
More than 150 human trials have tested resveratrol. Most found nothing. No supplement has been shown to make a person live longer.
8 trials asked whether NMN, NR, urolithin A or spermidine make the body work better. 1 met its goal. 1 passed a looser test.
Statins block the pathway that makes CoQ10. That part is true, and it is why the supplement exists. It is also not why your muscles hurt.
Only about 40 percent of people carry the gut bacteria that make urolithin A. Trials found about a 12 percent gain in leg strength, and several missed their main goal.
A 2023 taurine study extended mouse lifespan by about 10 percent. Its human half was a correlation, not a trial. Two 2025 studies found taurine does not fall with age.
The big one-gram heart trials found no detectable difference. Its reputation has a fifty-year head start on the data, beginning with 1970s Greenland studies.
A 2018 cohort of 829 people linked the highest dietary intake to 24 percent lower mortality over 20 years. The largest memory trial, in 100 adults, found nothing.
No head-to-head trial has found either one better. The deeper independent record belongs to one of them, and the most cited study of the other used 250 mg.
A 2024 Aging Cell study gave the flavonoid to aged mice and their arteries loosened. No human trial of vascular aging has reported yet.
Randomized trials show a rise of 40 to 100 percent in the blood. No large trial has shown a clinical benefit in healthy people.
For those interested in how female biology shapes aging
Most drugs are tested mainly on males. In the NIA testing program, 7 of 10 geroprotective drugs worked better in males, or only in males.
In more than 11,000 Bavarian monastics from 1890 to 1995 the advantage was at most one year. In the wider German population men fell behind instead.
The bone and lipid changes are measured and sharp. The epigenetic clock claim is not: no study has run one on the same women before and after menopause.
Canagliflozin added 14 percent to median lifespan in male mice. Females got three times more drug in their blood and no benefit at all.
Researchers studied 186 pairs of identical twins. The twin who got more sun looked older. Same genes, same age, different skin.