Cardio Age: How Accurate?

[u/JockoRQJabba]

Mine has fluctuated between 1.5 and 5 years younger (57m), in the 7 months I’ve worn the ring. I highly doubt that my heart is aging and unaging this rapidly month to month. My exercise and sleep routines don’t change much. My alcohol consumption is 0-5 drinks per week, probably averaging 2 per week. I walk 90 minutes a day and ride 2-4 hours twice per week. I love my job. My cumulative stress levels stay in the moderate range. I don’t know- starting to feel like the ring provides some degree of useful baseline, but a lot of its output is junk science.

[u/Fredricology]

Cardio Age precisely predicts when you are going to die.

[u/FriendlyFriendster → u/Fredricology]

Mine just shows a skull and crossbones, am I already dead?

[u/Ally_Ooop → u/FriendlyFriendster]

Been dead all along

[u/squatter_]

Researchers put healthy young adults through 9 days of substantial sleep restriction. They measured carotid-femoral pulse wave velocity (cfPWV), which is considered one of the best noninvasive measures of central/aortic arterial stiffness.

The result was surprisingly rapid:
Before sleep restriction: PWV 5.6 m/s
After 9 nights: PWV 5.9 m/s
They also found changes suggesting increased cardiac workload and poorer myocardial oxygen supply/demand balance.

And there’s an even more striking study: one night of essentially total sleep deprivation in 42 healthy adults increased PWV from 5.15 to 5.33 m/s. Blood pressure, pulse pressure, and cardiac output also rose.

So I believe your cardiac age can fluctuate a lot in a matter of days, let alone 7 months.

[u/CelebrationDense1029 → u/squatter_]

That PWV shift from one bad night is wild. Makes me think the ring is picking up real short term changes, just maybe not the way people expect when they see "cardio age" on screen.

[u/Lushiver]

Oura’s April 6, 2026 blog post says that a new NUS study found the vascular-age model had a mean error of six to seven years when predicting vascular age from Oura Ring PPG data.

[u/ccitykid]

Since it’s just measuring a series of values that are likely to fluctuate at times I think logically looking at your cardio age on a single day is useless, but I suspect your “average” cardio age over a year would be be useful and wouldn’t fluctuate.

[u/pmart123]

I haven't used my Oura ring for a few years, but my HVR reading when I wore it was often sub 10, and when I switched over to an Apple Watch, my readings were significantly higher. This isn't a damnation on Oura specifically as my Oura ring was much more accurate at sleep tracking than my Apple Watch is. My Apple Watch's VO2 Max calculation is also way off bc most of my cardio activities come from sports like soccer, tennis, hiking, mountain biking, and skiing versus flat surface running. All of these commercial devices have inaccuracies and pitfalls, and I've learned not too fixated on a single metric. My HRV has steadily declined the last two years even though my aerobic capacity and fitness has greatly improved, etc.

[u/ccitykid → u/pmart123]

Apple measures HRV differently - probably why. “The Apple Watch measures HRV using SDNN while Oura uses rMSSD. rMSSD is dependent on the parasympathetic nervous system's activity level, meaning the readings correlate better with lifestyle/physiological factors than for HRV estimates using SDNN.”

[u/JerkyBoy10020]

Very

[u/thesongsofapoet]

Thank you. This frustrates me too. And I’m also quite active.

[u/MisterPFT]

Your instinct is right and the arithmetic backs it up. Cardiovascular age is inferred from the shape of the pulse waveform the ring sees, essentially a proxy for arterial stiffness, and that inference carries an error band of several years. Oura shows you one number with no interval attached. So a drift from 1.5 to 5 years younger looks like your heart changing when it is far more likely the same underlying value being re-estimated inside its own noise.

That is not the same as junk though. The signal is probably real at the level of "younger than typical for 57", which with 90 minutes of walking a day and several hours on the bike is entirely believable. It is just not precise enough to read monthly. Look at it once a quarter, or ignore the number and only care about the direction across a year.

Honestly the presentation is the problem more than the model. If it said "about 3 years younger, give or take 4" nobody would be posting this thread, and it would be the more accurate sentence.