Aging and HRV: Reading Your Biological Age

In 1987, St. Louis, Missouri. Washington University cardiologist Robert Kleiger was analyzing data from 808 heart attack survivors. Two years of follow-up. Who lived and who died.

What he found was shocking.

Patients with low heart rate variability (HRV)—specifically, SDNN below 50ms—had mortality rates 5.3 times higher than those above 100ms.

Not 5 times. 5.3 times.

Kleiger published his paper: "Decreased heart rate variability and its association with increased mortality after acute myocardial infarction." It sent ripples through medicine, spawning decades of research on HRV and mortality.

The conclusion was consistent. Low HRV means higher probability of early death.

That may sound harsh. But there's good news too. HRV can be changed.

HRV Declines with Age

Let's start with the sad truth. HRV naturally decreases as you age.

If average RMSSD in your 20s is 50-60ms, by your 60s it's around 30-40ms. Some research suggests roughly 5-10% decline per decade. This happens to almost everyone.

Why?

Declining Vagal Tone

Parasympathetic activity, especially vagus nerve function, decreases with age. The vagus nerve is a massive neural network connecting heart, lungs, and digestive organs. When this system "loosens up," HRV drops.

Increased Arterial Stiffness

When blood vessels harden, the heart's response to blood pressure changes becomes sluggish. Baroreflex sensitivity decreases, and heart rate fluctuation narrows.

Sympathetic Dominance

With age, sympathetic activity tends to increase relatively. It's not just that parasympathetic weakens—sympathetic also becomes more active.

Cardiac Aging Itself

The heart's sinoatrial node (the pacemaker center) also ages. The heart's capacity to beat at varying speeds diminishes.

This can't be avoided entirely. But the rate can be slowed.

Biological Age vs. Calendar Age

The age on your driver's license and your body's age are different.

Two 50-year-olds: one's body functions like a 40-year-old's, another's is exhausted like a 60-year-old's. This is called "biological age."

HRV is one useful indicator for estimating biological age.

50 years old with HRV of 55ms? Much higher than the same-age average (roughly 35-40ms). Your body is operating young.

30 years old with HRV of 25ms? Much lower than the same-age average (roughly 50-55ms). A warning that your body is older than its years.

Chronic Stress Accelerates Aging

High-stress jobs, sleep deprivation, heavy drinking, smoking, sedentary lifestyle. These factors lower HRV and accelerate biological aging.

Conversely, good habits maintain or improve HRV and slow biological aging.

Mortality Prediction: Sobering Studies

Since Kleiger's 1987 study, countless follow-up research has accumulated. Conclusions are consistent.

Jarczok 2022 Meta-Analysis

A meta-analysis aggregating 38,000 people. Those with low HRV had 1.5-1.7 times higher all-cause mortality risk. Even after adjusting for age, sex, and smoking status.

Cardiovascular Mortality

For cardiovascular disease specifically, the gap widens further. In Kleiger's study, the group with SDNN below 50ms had 5.3 times higher mortality than those above 100ms.

In General Populations Too

Similar patterns appear not just in cardiac patients but in healthy general populations. The Copenhagen Heart Study tracked 653 healthy adults for 15 years. Low HRV correlated with increased cardiovascular event risk.

Why Does HRV Connect to Mortality?

HRV doesn't just reflect heart health. It reflects your body's overall "adaptability."

High HRV means:

Ability to recover quickly from stress
Good regulation of inflammatory responses
Balanced autonomic nervous system
Flexible cardiovascular function

Low HRV means all of these are impaired. A body vulnerable to stress, slow to recover, prone to disease.

The Inflammatory Reflex and Longevity

The vagus nerve connects directly to the immune system through what's called the "inflammatory reflex."

When the vagus nerve activates, it sends signals suppressing inflammation. Acetylcholine releases from spleen T-cells, inhibiting TNF-α (an inflammatory cytokine) production in macrophages.

Conversely, when the vagus nerve weakens, chronic inflammation increases.

Chronic inflammation is a common cause of nearly all age-related diseases:

Heart disease
Diabetes
Cancer
Alzheimer's disease
Arthritis
Age-related sarcopenia

This is why longevity researchers are excited about HRV. High HRV means good inflammation control. Good inflammation control means lower probability of those diseases.

HRV in Centenarians

What's the HRV like in people who live past 100 (centenarians)?

Interesting research exists. Centenarians sometimes show HRV higher than people in their 80s-90s. These "super agers" have relatively well-preserved autonomic nervous system function.

Establishing causation is difficult, of course. Did high HRV let them live long, or were they destined to live long and thus maintained HRV? Probably both.

But one thing is clear: there's a connection between longevity and HRV. And HRV can be changed through effort.

How to Maintain/Improve HRV

No need to give up because you're getting older. Research shows lifestyle improvements can significantly enhance HRV.

Regular Aerobic Exercise

The most powerful method.

It's no accident that marathon runners have HRV more than double that of average people. Regular aerobic exercise enlarges heart capacity, strengthens vagal tone, and reduces arterial stiffness.

What matters isn't "high intensity" but "consistency." Zone 2 training—intensity where you can "still hold a conversation"—three or more times weekly for 30-45 minutes. Maintain this for months and HRV rises.

Age is no excuse. In fact, the older you are, the more you need it.

Breathing Training

Six breaths per minute resonance breathing. Five seconds in, five seconds out.

Meta-analyses show practicing 3-5 times weekly for 10-20 minutes over 4-12 weeks improves baseline HRV. Effectiveness is proven even in older adults.

A 2018 study by Prinsloo analyzed HRV biofeedback effects in older adults. Depression reduction effect size Cohen's d = 1.02, anxiety reduction 0.82-0.84, attention improvement 1.00. All very large effects.

Sleep Optimization

HRV recovers during sleep. Without adequate sleep, no recovery.

Sleep quality tends to decline with age. Deep sleep decreases, and you wake frequently. This can accelerate HRV decline.

Basic sleep hygiene principles:

Go to bed and wake at the same time daily
Bedroom temperature 64-72°F (18-22°C)
Avoid smartphones/blue light before bed
No caffeine in the afternoon
Reduce alcohol (impairs sleep quality)

Stress Management

Chronic stress erodes HRV. When the sympathetic system stays constantly active, the vagus nerve is suppressed.

Stress can exist even in retirement. Financial worries, health concerns, social isolation. These accumulate and drop HRV.

Hobbies, social connection, meaningful activities. These reduce stress and help maintain HRV.

Nutrition

Research suggests the Mediterranean diet benefits cardiovascular health and HRV. Fruits, vegetables, fish, olive oil, nuts.

Evidence for specific supplements is limited, but some research suggests omega-3 fatty acids may positively affect HRV.

Quit Smoking

Smoking lowers HRV. Quitting allows gradual recovery.

Limit Alcohol

Alcohol lowers HRV during sleep and interferes with deep sleep. No need to quit entirely, but many experts recommend no more than 2 drinks per week.

Tracking Aging with Wearables

Wearables like Apple Watch, Oura Ring, and Garmin allow long-term HRV tracking.

Understanding Your Aging Rate

Gather a year of HRV data. Is your annual average rising, maintaining, or falling?

Normal aging might show about 3-5% annual decline. But lifestyle improvements can offset this decline or even reverse it.

Measuring Intervention Effects

When you start exercising, begin breathing training, or improve sleep—data confirms whether it's working.

"Started exercising 3 months ago, and my 3-month average HRV is up 10% compared to the previous 3 months. It's working."

Early Warning

If HRV suddenly drops or shows persistent declining trends, something may be wrong.

Has sleep quality declined?
Has stress increased?
Is there a health issue?

You can objectively assess your body's state before even seeing a doctor.

Cognitive Function and HRV

What's most feared in aging may be mental rather than physical. Memory decline. Dementia.

Interestingly, there's also a connection between HRV and cognitive function.

2025 Umbrella Review

An umbrella review synthesizing 21 meta-analyses reported "suggestive evidence" that dementia is associated with HRV decline. 442 primary studies, 34,625 participants.

Mechanism

The vagus nerve also connects to the brain. High vagal tone:

Suppresses brain inflammation
Improves cerebral blood flow
Promotes neuroplasticity

Low HRV may be a negative signal for brain health too.

Cognitive Effects of HRV Biofeedback in Older Adults

In the previously mentioned Prinsloo 2018 study, older adults showed significantly improved attention test (Trail Making Test-A) scores after HRV biofeedback. Effect size Cohen's d = 1.00.

Breathing training may also help maintain cognitive function.

Can You Raise HRV at 80?

Yes. Research shows exercise and breathing training can improve HRV regardless of age.

You won't reach 20-something levels, of course. Completely reversing age-related baseline decline is difficult. But you can slow the rate of decline and maintain levels above your same-age average.

More importantly, it's not too late to start now.

Starting exercise at 60 still works. Starting breathing training at 70 still works.

Don't think "At my age, what's the point..." The data tells you. It works.

What Do Longevity Experts Do?

Longevity medicine pioneer Peter Attia writes in his book Outlive:

"There are two components to longevity. Lifespan and healthspan. Living long matters, but living long in good health matters more."

He emphasizes:

Exercise: Especially the combination of aerobic and strength training
Sleep: 7-8 hours of quality sleep
Nutrition: Avoiding overeating, quality protein
Emotional health: Stress management, relationships
Metabolic health: Blood sugar, insulin resistance management

All of this reflects in HRV. HRV is a composite indicator showing how well these factors are integrated and functioning.

Stanford neuroscientist Andrew Huberman says:

"The key to stress management is having tools to regulate the autonomic nervous system in real-time."

His recommended tools:

Physiological sigh (two nasal inhales, long exhale through mouth)
Six breaths per minute resonance breathing
Cold exposure
Morning sunlight

Simple. No special equipment or cost required. You can start today.

Beyond the Numbers

If you've read this far, you understand HRV is more than just a number.

HRV shows your body's "adaptability." The ability to recover from stress, flexibility in responding to change, overall system health.

HRV declining with age is natural. But the speed of decline is a matter of choice.

Walking 30 minutes daily. 10 minutes of breathing training daily. 7 hours of sleep. Reducing alcohol and tobacco.

These "boring" choices accumulate, and in 10 years your HRV will be different. Your biological age will be different. Your quality of life will be different.

What Kleiger discovered in 1987 wasn't just a medical fact. It was proof that our bodies constantly communicate their state—and responding to those signals changes outcomes.

This morning, what was your HRV?

And in one year, what do you want that number to become?

The choice starts today.

References

Mortality Research

Kleiger, R.E., et al. (1987). Decreased heart rate variability and its association with increased mortality after acute myocardial infarction. American Journal of Cardiology.
Jarczok, M.N., et al. (2022). Heart rate variability in the prediction of mortality: A systematic review and meta-analysis. Neuroscience & Biobehavioral Reviews.

Aging and HRV

Umetani, K., et al. (1998). Twenty-four hour time domain heart rate variability and heart rate: relations to age and gender over nine decades. Journal of the American College of Cardiology.
Antelmi, I., et al. (2004). Influence of age, gender, body mass index, and functional capacity on heart rate variability in a cohort of subjects without heart disease. American Journal of Cardiology.

Inflammatory Reflex

Tracey, K.J. (2002). The inflammatory reflex. Nature.
Pavlov, V.A., & Tracey, K.J. (2012). The vagus nerve and the inflammatory reflex—linking immunity and metabolism. Nature Reviews Endocrinology.

HRV Interventions in Older Adults

Prinsloo, G.E., et al. (2018). Heart rate variability biofeedback: implications for cognitive and psychiatric effects in older adults. Applied Psychophysiology and Biofeedback.
Ghiya, S. (2022). Effect of Resonance Breathing on Heart Rate Variability and Cognitive Functions in Young Adults. Journal of Family Medicine and Primary Care.

Longevity

Attia, P. (2023). Outlive: The Science and Art of Longevity. Harmony Books.
Huberman Lab Podcast: Various episodes on stress management and longevity.

Cognitive Function and HRV

Heart rate variability in mental disorders: an umbrella review of meta-analyses. (2025). Translational Psychiatry, 15, 39.