HRV by age: normal ranges from peer-reviewed research

Search for “normal HRV by age” and you’ll find a dozen charts, all slightly different, almost none of them telling you where the numbers came from. That’s a problem, because HRV is one of the most context-dependent numbers in consumer health. The same person, measured three ways on the same day, will produce three different values.

This article, by contrast, does it differently. Every number below comes from peer-reviewed research, with the study, the method and the sample size attached, and a link so you can check it yourself. Moreover, I’ll be clear about which numbers I could verify directly and which I couldn’t.

One warning up front, and it matters more than any table here: if you track HRV on a wrist wearable overnight, the published charts do not apply to you directly. I’ll explain why near the end.

What HRV is

Heart rate variability is the variation in time between consecutive heartbeats. Your heart doesn’t tick like a metronome — a healthy, well-recovered nervous system constantly adjusts the timing beat to beat. That variation reflects the balance between the two branches of your autonomic nervous system: the sympathetic (“fight or flight”) and parasympathetic (“rest and digest”) arms.

More variation generally means more parasympathetic activity, which is what recovery looks like. Conversely, stress, poor sleep, alcohol, illness and overtraining all flatten it. In short, it’s a recovery and stress marker rather than a fitness score — and it’s deeply individual.

The two numbers you’ll see: RMSSD and SDNN

Most confusion about HRV comes from people comparing different metrics as if they were the same thing.

RMSSD (root mean square of successive differences) captures beat-to-beat changes and mainly reflects parasympathetic, vagal activity. As a result, it’s what almost every consumer wearable reports, and it’s reasonably stable over short recordings.

SDNN (standard deviation of normal-to-normal intervals) captures total variability from all sources. However, it’s strongly influenced by recording length, so a 24-hour SDNN is far larger than a 5-minute SDNN — they aren’t comparable.

One useful conversion: if a study reports SD1 from a Poincaré plot, that’s the same information as RMSSD. SD1 = RMSSD ÷ √2, so RMSSD = SD1 × √2.

HRV by age: the reference table

The best age-stratified dataset for short recordings comes from Voss and colleagues, published in PLOS ONE in 2015. They analysed 5-minute supine resting ECGs from 1,906 carefully screened healthy adults in the population-based German KORA S4 cohort — 782 women and 1,124 men, aged 25 to 74.

Here are the actual values, mean ± standard deviation:

Age group	RMSSD women	RMSSD men	SDNN women	SDNN men
25–34	42.9 ± 22.8 ms	39.7 ± 19.9 ms	48.7 ms	50.0 ms
35–44	35.4 ± 18.5 ms	32.0 ± 16.5 ms	45.4 ms	44.6 ms
45–54	26.3 ± 13.6 ms	23.0 ± 10.9 ms	36.9 ms	36.8 ms
55–64	21.4 ± 11.9 ms	19.9 ± 11.1 ms	30.6 ms	32.8 ms
65–74	19.1 ± 11.8 ms	19.1 ± 10.7 ms	27.8 ms	29.6 ms

First, look at those standard deviations before you compare yourself to anything. In the 45–54 group, one standard deviation is half the mean. In other words, the spread between healthy people of the same age is enormous — which is exactly why a single “good HRV” number for your age doesn’t really exist.

For a broader benchmark that isn’t age-split: a systematic review by Nunan and colleagues pooled 44 studies covering 21,438 healthy adults and reported a short-term RMSSD of roughly 42 ms (range across studies 19–75) and SDNN of 50 ± 16 ms (range 32–93).

Why HRV falls with age — and why it stops falling

Indeed, the decline is one of the most consistent findings in autonomic physiology. Structurally, you lose sinoatrial pacemaker cells and arterial elasticity; functionally, the coupling between regulatory systems degrades.

But the shape of that decline is more interesting than the fact of it.

Specifically, Voss found the steepest drop between the 35–44 and 45–54 groups. After that it flattens — and between 55–64 and 65–74 there was no statistically significant difference at all. Consequently, the authors concluded that from around 55 onwards, distinguishing between the older age decades serves little purpose.

Moreover, the 24-hour data agrees. Umetani and colleagues, studying 260 healthy people aged 10 to 99 with Holter monitoring, found RMSSD declined fastest early in life, reaching about 47% of young-adult baseline by the sixth decade — and then stabilising.

That’s genuinely useful news if you’re in your fifties: the steep part is behind you. Therefore, what you see moving now is mostly not age.

What about sex differences?

In practice, smaller than most people assume — and they fade. In the Voss data, RMSSD and SDNN showed no significant difference between men and women within the age decades, while the gender differences that did exist across other metrics had largely disappeared by the 55–64 group. Below age 30, women tend to show lower HRV than men on several measures; by 50, however, the gap has closed.

The measurement problem nobody mentions

Here’s why HRV charts disagree with each other. For example, the Baependi Heart Study measured 543 healthy adults three ways:

Same people. Same day. RMSSD of 39 ms on 24-hour Holter, 36 ms lying down, and 21 ms standing. Nothing about their physiology changed — only the method.

So before you compare your number to any chart, ask: was it 24-hour Holter, 5-minute supine ECG, or something else? If the article doesn’t say, the chart is useless.

If you use a wearable, read this part twice

This is the section most HRV articles skip, and it’s the one that matters most for anyone with a Whoop, Oura, Garmin or Polar.

Your device measures at night. Overnight RMSSD runs higher than daytime resting values, because vagal tone dominates during sleep. Therefore, comparing a nightly wearable reading to the daytime resting-ECG table above will flatter you — the numbers are on different scales.

And the devices disagree with ECG, by different amounts. A 2025 validation study in Physiological Reports put five wearables against an ECG reference across 536 nights. For HRV, the Oura rings were closest (Gen 4 concordance 0.99), followed by Whoop (0.94) and Garmin (0.87). The Polar device tested came last, with a concordance of 0.82 and a mean absolute percentage error above 16%.

Admittedly, two caveats apply: the study used 13 participants, and the Polar model was the Grit X Pro, not every Polar watch. Nevertheless, the direction is clear enough — wrist PPG is not ECG.

The practical conclusion: your absolute number is not comparable to the research tables, but your own trend is still valid. Systematic device error largely cancels out when you compare yourself to yourself with the same device. Instead, track your baseline over 30–60 days and watch the direction of travel. Alternatively, if you want a genuinely comparable number, take an occasional 5-minute supine morning reading with a validated chest strap — that’s the format the research uses.

Does low HRV mean heart trouble?

At population level, low HRV really does flag higher risk. A meta-analysis by Hillebrand and colleagues in Europace pooled eight studies covering 21,988 people with no known cardiovascular disease and found that the lowest SDNN group had a pooled relative risk of 1.35 (95% CI 1.10–1.67) for a first cardiovascular event — the widely quoted “32 to 45% higher risk”. Similarly, the ARIC community cohort found each standard deviation lower SDNN was associated with roughly 24% higher risk of sudden cardiac death, while the Framingham data showed reduced HRV predicted cardiac events beyond standard risk factors.

Now the crucial caveat. In 2023, a UK Biobank analysis of 46,075 people published in Communications Biology found that while measured HRV predicted mortality, genetically predicted HRV did not. That’s a strong hint that low HRV is largely a marker of underlying health, fitness and stress rather than a cause of disease in its own right.

In short, chasing a higher HRV number is not the same as lowering your risk. HRV is a useful mirror, not a lever you pull directly. Above all, it is never a diagnosis — if you’re worried about your heart, that’s a conversation with a doctor, not a wearable.

What actually raises HRV

So far, three interventions have decent evidence behind them.

Aerobic exercise. A 2022 systematic review with meta-analysis in previously sedentary adults found training produced a small but significant increase in RMSSD (SMD 0.57, 95% CI 0.23–0.91) and in high-frequency power.

Slow breathing. Likewise, a 2022 meta-analysis in Neuroscience & Biobehavioral Reviews concluded that voluntary slow breathing — around six breaths per minute — increases parasympathetic control of the heart, with RMSSD rising during, immediately after, and after the intervention period.

Cutting evening alcohol. Controlled polysomnography work shows pre-sleep alcohol raises nocturnal heart rate, suppresses vagal HRV and increases sympathetic activity. So if your wearable HRV crashes some nights, look at what you drank.

Finally, sleep quality sits underneath all three — and it’s the one most people neglect while buying supplements.

Frequently asked questions

What’s a good HRV for my age?

Unfortunately, there isn’t one clean answer. For a 55-year-old man, the daytime resting-ECG reference is roughly 20 ms RMSSD, but the healthy spread is so wide that being above or below it means little on its own. Instead, your own baseline and trend are far more informative.

Why is my watch’s number so much higher than these tables?

Because it measures overnight, when vagal tone is highest, and because wrist optical sensors read differently from ECG. Therefore, don’t compare the two.

How much day-to-day variation is normal?

Quite a lot, in fact. Single nights are noise. Instead, look at a 7-day rolling average; a sustained drop of around 20% from your own baseline is the signal worth investigating.

Can I improve my HRV at 55?

The steep age-related decline mostly happens before your fifties, so yes — what moves after that is largely lifestyle. For instance, aerobic training, slow breathing and better sleep all have supporting evidence.

References

Reference values and measurement standards

• Voss A, Schroeder R, Heitmann A, Peters A, Perz S. Short-term heart rate variability — influence of gender and age in healthy subjects. PLOS ONE 2015;10(3):e0118308. PMID 25822720
• Nunan D, Sandercock GRH, Brodie DA. A quantitative systematic review of normal values for short-term heart rate variability in healthy adults. Pacing Clin Electrophysiol 2010;33(11):1407–1417. PMID 20663071
• Umetani K, Singer DH, McCraty R, Atkinson M. Twenty-four hour time domain heart rate variability and heart rate: relations to age and gender over nine decades. J Am Coll Cardiol 1998;31(3):593–601. PMID 9502641
• Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Heart rate variability: standards of measurement, physiological interpretation and clinical use. Circulation 1996;93:1043–1065. PMID 8598068
• Age and sex differences in heart rate variability and vagal specific patterns — Baependi Heart Study. Global Heart 2021. DOI 10.5334/gh.873
• Dial MB, Hollander ME, Vatne EA, Emerson AM, Edwards NA, Hagen JA. Validation of nocturnal resting heart rate and heart rate variability in consumer wearables. Physiological Reports 2025;13(16):e70527. PMID 40834291

Cardiovascular risk and modifying HRV

• Hillebrand S, et al. Heart rate variability and first cardiovascular event in populations without known cardiovascular disease: meta-analysis and dose–response meta-regression. Europace 2013;15(5):742–749. PMID 23370966
• Tsuji H, et al. Impact of reduced heart rate variability on risk for cardiac events. The Framingham Heart Study. Circulation 1996;94(11):2850–2855. PMID 8941112
• Phenotypic but not genetically predicted heart rate variability associated with all-cause mortality. Communications Biology 2023;6:1131. DOI 10.1038/s42003-023-05376-y
• Casanova-Lizón A, et al. Does exercise training improve cardiac autonomic nervous system function in sedentary adults? A systematic review and meta-analysis. Int J Environ Res Public Health 2022;19(21):13899. PMC9656115
• Laborde S, et al. Effects of voluntary slow breathing on heart rate and heart rate variability: a systematic review and meta-analysis. Neurosci Biobehav Rev 2022;138:104711. PMID 35623448

A note on sourcing: the Voss values above were taken directly from the published paper. However, Umetani’s exact per-decade figures sit in a paywalled table, so only the decline pattern and percentages are cited here, not specific decade values. Finally, the often-repeated claim that SDNN falls “about 1% per year” could not be traced to a verifiable primary source and is therefore not used.

This article is general information, not medical advice.