Miscellaneous News

Saliva vs Blood Tests for Biological Age: Which One Actually Works?

Published

1 year ago

June 12, 2025

A new saliva-based epigenetic clock offers a fast, affordable way to estimate biological age, but how does it compare to blood-based aging tests like Blueprint?

Today, a new study introduced a 10-CpG saliva test that claims it can estimate your biological age with just a spit sample. Researchers analyzed DNA methylation patterns from over 3,400 people and found that just ten specific sites in your saliva can predict your age with surprising accuracy. It’s cheap, non-invasive, and fast. However, how does this compare to blood-based tests like Blueprint’s Speed of Aging test, which we’ve already used and plan to use again later this year?

Let’s break it down.

What the 10-CpG Saliva Clock Measures

This new study, published in DNA in June 2025, describes a minimalist epigenetic clock built from just 10 CpG sites in saliva DNA. These are regions in your genome where methylation, a chemical modification that changes with age, can be measured.

The researchers found that this small set of sites could predict a person’s chronological age with a correlation of 0.80 and a mean error of around 5.5 years. In other words, if you’re 45, the test might guess you’re anywhere from 40 to 50.

It’s based on data from healthy individuals aged 15 to 89 and uses the Illumina EPIC 850k array to detect age-related hypermethylation patterns in genes related to metabolism, cognitive function, and hormone signaling.

How It Compares to Blueprint’s Speed of Aging Test

We’ve done the Speed of Aging test through Blueprint. It required a simple finger prick and a few drops of blood on a sample card. That blood was then used to calculate our biological rate of aging, not just our age.

Unlike the saliva test, which estimates how old you are, Blueprint’s blood-based test (built on the DunedinPACE algorithm) tells you how fast you’re aging at a cellular level. A score of 1.00 means you’re aging biologically one year per calendar year. A score below 1.00 means you’re slowing the clock.

These blood-based tests use over 100 CpG markers and are trained on decades of longitudinal health data, giving them more depth and better predictive power for things like disease risk, cognitive decline, and overall healthspan.

When to Use a Saliva Test

The saliva clock is compelling, because it’s easy and low-cost. It doesn’t require a blood draw or even a finger prick. That makes it a great entry point for tracking biological age, especially for those who are curious but not ready to invest in more advanced diagnostics.

It could also be a useful tool for broad population screening or longitudinal tracking when cost and convenience are priorities.

However, it’s important to note what it is not. It does not measure your pace of aging. It cannot tell you if your lifestyle changes are working. And while it highlights some genes that are biologically meaningful, it lacks the depth and validation that DunedinPACE and Blueprint offer.

Use Case Comparison

Scenario	10-CpG Saliva Clock	DunedinPACE / Blueprint Speed of Aging
Quick, non-invasive test	✅ Yes	❌ Requires blood
Low-cost or consumer health tracking	✅ Ideal	❌ More expensive, lab dependent
Longitudinal rate of aging tracking	❌ Not designed for this	✅ Gold standard for tracking pace of aging
Used in research predicting mortality/disease	❌ Not yet	✅ Extensively validated
Useful for lifestyle intervention testing	⚠️ Limited sensitivity	✅ Highly responsive to lifestyle changes
Blueprint’s internal model	❌ No (Blueprint uses DunedinPACE)	✅ Yes – Blueprint’s “Speed of Aging” is based on DunedinPACE

Our Take on the Science

After researching the two, here’s where things get interesting. The ten CpG sites in this saliva test are associated with genes like ELOVL2 (linked to fat metabolism and eye health), CHGA (tied to blood pressure), and GPR158 (involved in mood and cognition). That gives this clock biological credibility.

But the test is limited to measuring DNA from saliva, which includes a mix of epithelial and immune cells, not the full systemic picture that blood can provide.

Blood tests like Blueprint are better suited for identifying whether you are aging faster or slower than average, and they have been linked to real-world outcomes like cardiovascular disease, dementia risk, and mortality.

Accuracy and Scientific Depth

Feature	10-CpG Saliva Clock	DunedinPACE / Speed of Aging (Blood)
Input	Saliva DNA (non-invasive)	Blood DNA (invasive)
Markers Used	10 CpG sites	~173 CpG sites
Primary Output	Predicted biological age	Biological aging rate (relative to normal pace)
Correlation to Chronological Age	r = 0.80 (good)	Not designed to predict age, but pace (biological drift)
Mean Absolute Error	~5.5 years	N/A – not estimating age, but speed
Scientific Foundation	Cross-sectional saliva DNA data	Longitudinal 20-year Dunedin cohort + functional healthspan outcomes
Predictive Power for Health Outcomes	Moderate (saliva age proxy)	High – associated with morbidity, mortality, cognitive decline, fitness decline, etc.

Final Thoughts

The new saliva-based epigenetic clock is an exciting development. It opens the door to wider access and mainstream curiosity around biological aging. If all you want is a rough estimate of your biological age without pricking your finger, it’s a good starting point.

But if you’re serious about understanding the trajectory of your health and longevity, and whether your lifestyle changes are working, blood-based models like Blueprint’s Speed of Aging test remain the gold standard.

We’ll be doing another blood-based test later this year to see if our lifestyle upgrades are slowing the clock. Until then, we’re keeping an eye on how these simpler models evolve and what they might tell us about the biology of aging, one molecule at a time.

🩺 Disclaimer

The content on I Won’t Die is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with any health concerns.

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Miscellaneous News

Download the New I Won’t Die App: Longevity News, Biohacking Insights, and Health Tools

Published

2 months ago

May 18, 2026

Sean Callahan

A faster, rebuilt iPhone app for curated longevity news, Bryan Johnson and Blueprint commentary, biomarker insights, fitness, recovery, nutrition, and practical health optimization.

The new I Won’t Die iOS app is now available.

It has been rebuilt as a faster, fully native iPhone experience. The app helps you follow longevity news, biohacking insights, and practical health optimization.

Inside, you can read curated articles on healthspan, biomarkers, fitness, recovery, sleep, nutrition, and performance. Coverage also includes Bryan Johnson, Blueprint, the Blueprint protocol, and the Don’t Die movement.

This update brings a cleaner Home screen with featured articles, latest posts, topics, and health tools. Articles now open in a polished native reading view. You can save posts, share articles, explore related content, and open links more easily.

Image handling, article formatting, and overall performance have also been improved. You can also turn on push notifications for newly published articles.

The goal is simple: stay informed without the clutter. No noisy popups. No distractions. Just curated longevity and health content in a clean app built for light mode and dark mode.

Whether you follow Bryan Johnson and Blueprint, or simply care about better health, the app keeps things focused. It is built for curious readers, biohackers, fitness-minded people, and anyone working toward a healthier life.

Download the new iOS app here:
https://apps.apple.com/us/app/i-wont-die/id6745723273

The Android version is also available, with the new update coming later:
https://play.google.com/store/apps/details?id=appiwontdiecom.wpapp

🩺 Disclaimer

🚀 Get Started with Blueprint

Start optimizing your health today with $25 off your first order! Use our referral code to begin your Blueprint journey and take control of your longevity.

🏋️‍♂️ Track Your Sleep, Workouts & Recovery

Boost your performance and recovery with Whoop. Join with my referral link to get a free WHOOP 5.0 and one month free!

📲 Download the I Won’t Die App

Stay ahead with the latest news, updates, and insights. Download the I Won’t Die app now on the Apple App Store and Google Play!

📩 Contact Us

Have tips, photos, or questions? Want to collaborate? Reach out at [email protected] — we’d love to hear from you!

🔗 Stay Connected

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Miscellaneous News

Stop Guessing Your Run: StayGreen Turns WHOOP Data Into Today’s Training Decision

Published

3 months ago

May 4, 2026

Sean Callahan

Know exactly how to run today with recovery-aware coaching built specifically for runners who use WHOOP.

Runners are great at collecting data.

We have watches, heart-rate zones, recovery scores, sleep scores, strain targets, pace charts, weekly mileage, training plans, and enough graphs to make a NASA engineer feel seen. 🚀

I do it daily using multiple apps and with my WHOOP device.

But there is one question most runners still ask almost every day, including myself:

What should I actually do today?

That is exactly why I built StayGreen: Run Coach for WHOOP, a new iOS app designed specifically for runners who use WHOOP and want clearer, smarter, more actionable run guidance.

StayGreen takes your WHOOP recovery, sleep, strain, HRV, resting heart rate, physiological cycle data, and recent running history, then turns all of that signal into one focused daily run call.

Not a dashboard full of numbers, a vague “listen to your body,” or a general strain target.

A real running decision.

Should you run easy? Keep it aerobic? Move the long run? Take a recovery walk? Protect the week? Use today as a controlled quality window?

StayGreen is built to help you know in about five seconds.

Why StayGreen Exists

WHOOP gives runners powerful data. Recovery, strain, sleep, HRV, resting heart rate, workouts, and physiological trends can all tell you something important.

But runners do not just need more metrics.

They need translation.

Because a green recovery does not always mean “go crush yourself.” A yellow day does not always mean “do nothing.” A red day might not mean the week is ruined. And sometimes the smartest training move is not the hardest one, but the one that keeps tomorrow alive.

StayGreen sits on top of your WHOOP data and adds a running-specific coaching layer.

It looks at your baseline, your recent runs, your weekly load, your hard-effort spacing, your long-run timing, and the cost of your recent training. Then it answers the practical question runners care about most:

How should I run today?

The Daily Run Call

At the center of StayGreen is the Daily Run Call.

This is your simple, readable recommendation for the day. It brings together recovery, sleep, strain, HRV-informed readiness, recent running load, and your current running goal.

You might see guidance like:

Run easy.
Keep it aerobic.
Move the long run.
Take a recovery walk.
Protect the week.
Use today as a controlled quality window.

The goal is not to make every green day bigger. The goal is to train with better timing, better restraint, and better awareness of how today affects tomorrow.

That is the idea behind the name StayGreen. It is not about chasing green harder or turning every good recovery day into a test. It is about staying consistent, durable, and ready for the next run.

For me personally, that means longevity running: a daily seven-mile rhythm where the goal is not to empty the tank, but to finish feeling strong, recover well, and wake up ready to do it again.

Meet Run Reserve

StayGreen also introduces a simple score called Run Reserve.

Run Reserve helps answer: “How much running capacity do I have today?”

It is not just a recovery score. It is a running-readiness signal that considers your WHOOP data alongside recent training load, sleep, strain, and baseline trends.

A high Run Reserve might mean you have room to extend, build, or execute the plan.

A lower Run Reserve might mean the better move is to keep things easy, shorten the run, or protect the rest of the week.

It gives runners a practical way to understand capacity without needing to interpret every underlying metric manually.

The Coach Behind the Decision

StayGreen is free to download and includes core daily guidance, but runners who upgrade to Run Coach Pro unlock the AI coaching layer behind the decisions.

That is where the app gets even more useful.

Run Coach Pro adds AI-assisted coach notes that explain what to do, why it matters, and the mistake to avoid. Instead of only seeing the recommendation, you get the reasoning behind it.

For example, StayGreen might tell you that today is better suited for aerobic work because your weekly load is already climbing, your last hard effort is still recent, and your recovery is good enough to move but not ideal for forcing intensity.

That kind of context helps you train smarter, not just obey a score.

Post-Run Coaching That Actually Teaches You Something

A lot of running apps are built around what happened.

StayGreen is built around what it means.

After a run, StayGreen looks at the effort and helps you understand whether you protected the week, spent too much, or kept the run right where it needed to be.

It can identify when an easy run quietly turned into a workout, show when a run was controlled enough to support tomorrow, and help you understand what today’s effort may have cost your body and how it affects your next decision.

That is especially helpful for runners who love to push, because the line between “easy” and “accidentally spicy” can get blurry fast.

Weekly Coaching and Hidden Patterns

StayGreen is not only about today.

The app also helps you understand your week.

With Run Coach Pro, you can unlock weekly coach reads and running pattern insights that look at rolling load, intensity mix, long-run readiness, normal range, and trends that are easy to miss.

Maybe your base runs are getting smoother, while your easy days are quietly drifting too hard. Maybe your weekly load is climbing faster than your recovery can support, or the terrain, heat, hills, and pacing patterns are making certain runs more expensive than expected.

StayGreen helps surface those patterns so you can make better choices before your body has to send the message louder.

Built Around Your Goal

StayGreen adapts its recommendations based on what kind of runner you are trying to be right now.

You can use it for:

Build Base
Improve Speed
5K and 10K training
Half Marathon training
Marathon training
Longevity Running
Return to Running
Maintain Fitness

Whether you are coming back carefully, building durability, chasing a race goal, or simply trying to run consistently without burning out, StayGreen helps interpret your WHOOP data through the lens of your actual running goal.

Free vs. Run Coach Pro

StayGreen is free to download.

The free version includes your daily WHOOP-powered run call, Run Reserve score, basic post-run recap, basic weekly load, and limited coach note previews.

Run Coach Pro unlocks the deeper coaching layer, including AI Run Coach Notes, Post-Run Coach Notes, Weekly Coach Reads, Running Pattern Insights, full history, long-run guidance, Training Cost, and regenerated coach notes.

So you can start with the simple daily decision, then upgrade when you want the coach behind the call.

Who StayGreen Is For

StayGreen is for runners who use WHOOP and want their recovery data to become more actionable.

Use it when you wake up wondering whether today should be easy or hard.

Bring it into your training when you are preparing for a 5K, 10K, half marathon, or marathon and want to avoid blindly stacking fatigue.

Rely on it when consistency matters more than hero workouts.

Open it when you love data, but really want decisions.

Most of all, StayGreen is for runners who want to train better with restraint, because the best run is not always the hardest run.

Sometimes the best run is the one that keeps the week alive.

Download StayGreen for iOS

StayGreen: Run Coach for WHOOP is available now for iPhone.

Download it here:
https://apps.apple.com/us/app/staygreen-run-coach-for-whoop/id6762893528

StayGreen is independent and not affiliated with, endorsed by, or sponsored by WHOOP.

🩺 Disclaimer

🚀 Get Started with Blueprint

Start optimizing your health today with $25 off your first order! Use our referral code to begin your Blueprint journey and take control of your longevity.

🏋️‍♂️ Track Your Sleep, Workouts & Recovery

Boost your performance and recovery with Whoop. Join with my referral link to get a free WHOOP 5.0 and one month free!

📲 Download the I Won’t Die App

Stay ahead with the latest news, updates, and insights. Download the I Won’t Die app now on the Apple App Store and Google Play!

📩 Contact Us

Have tips, photos, or questions? Want to collaborate? Reach out at [email protected] — we’d love to hear from you!

🔗 Stay Connected

📬 Subscribe to I Won’t Die Newsletter

Get the latest longevity breakthroughs, Blueprint updates, and exclusive content straight to your inbox — sign up now!

Miscellaneous News

Fireworks, Freedom, and Fallout: What July 4th Is Doing to Your Body and Brain

Published

1 year ago

July 5, 2025

Sean Callahan

America’s favorite celebration comes with a hidden cost and that is air pollution, brain damage, and toxic exposure that rivals chain smoking.

Today, we recover from celebrating America’s birthday with fireworks and from inhaling the consequences. Yes, we’re talking about air quality outdoors post celebration.

Every year on July 4th, skies across the United States explode with color. It’s a tradition rooted in pride, patriotism, and the pursuit of happiness. However, while we celebrate our freedom, our bodies quietly absorb the cost.

Bryan Johnson recently shared what that cost looks like. According to his air quality monitors, PM₂.₅ levels during fireworks reached 160 micrograms per cubic meter, the equivalent of smoking a full cigarette in just one evening. In some areas, the air was as toxic as smoking 20 cigarettes. That’s not just patriotic, it’s poisonous.

Fireworks and Fine Particulates

Fireworks release a cocktail of harmful pollutants, including particulate matter (PM₂.₅), heavy metals like strontium and barium, and ultrafine soot. PM₂.₅ is especially concerning because it’s small enough to enter your lungs, bloodstream, and even cross the blood–brain barrier, potentially impacting brain health.

According to the EPA and NIH, exposure to PM₂.₅ has been linked to:

Increased risk of cardiovascular disease
Declines in cognitive function
Higher rates of depression and anxiety
Disruption of immune and cancer surveillance systems

In other words, these celebrations aren’t just loud, they’re neurotoxic.

It Doesn’t Stop in the Sky

What goes up must come down. Firework residue settles into our soil and water, where it contaminates food sources and drinking water. These heavy metals and chemicals don’t vanish after the show. They linger, bioaccumulate, and eventually make their way into our bodies again through food and water.

Fireworks are also a major cause of wildlife stress, asthma flare-ups, and ER visits during holiday weekends. The environmental and public health burden is significant, but we Americans love our fireworks to celebrate our country’s birthday.

Your Home Is a Sanctuary, If You Treat It Like One

Bryan’s data also shows that air quality inside his home remained dramatically better than outside during the fireworks, thanks to airtight building design, air purifiers, and filtered HVAC systems. In contrast, most homes without filtration offer little protection. Outdoor toxins easily infiltrate through vents, windows, and poorly sealed walls.

You can reduce your exposure with:

HEPA or carbon-based air purifiers
Keeping windows closed on high-pollution days
Monitoring air quality with tools like PurpleAir or IQAir
Using filtered masks if outdoors during high PM events

Alcohol and the Holiday Hangover

Bryan also called out another July 4th staple: alcohol. While drinking might seem like part of the fun, it comes with its own list of problems:

It impairs neurogenesis and cognitive function
Weakens immune response and cancer surveillance
Disrupts sleep cycles
Increases risk of depression and brain inflammation

So while it may feel like “letting loose,” you’re actually doing more long-term damage than you might think. Plain and simple. Don’t drink alcohol.

Final Thoughts

Our traditions mean something. They connect us to history, to each other, and to a shared sense of identity. However, if we’re honest, some of these customs are outdated and damaging, especially when we have the data to prove it.

This isn’t about canceling fireworks or outlawing alcohol. It’s about being informed. If we can send rockets into the sky to dazzle the nation, we can also find ways to celebrate without poisoning the air, water, and ourselves. Maybe it’s time to embrace drone-only firework displays on the 4th of July!

Let’s find ways to celebrate freedom that don’t come at the cost of our health. The future deserves clean air, conscious choices, and the kind of optimism that builds smarter traditions. Can patriotism shine just as brightly without the explosions? Share your thoughts in the comments below. 🎆

🩺 Disclaimer

🚀 Get Started with Blueprint

Start optimizing your health today with $25 off your first order! Use our referral code to begin your Blueprint journey and take control of your longevity.