You'll encounter "lung age" in smoking cessation materials, health screenings and a certain amount of supplement marketing. It sounds like a measurement. It's closer to a translation, and knowing the difference is useful — both for taking it seriously where it deserves to be and for ignoring claims built on it.
Where the number comes from
It starts with spirometry, the standard breathing test. You take the deepest breath you can and blow out as hard and fast as possible. Two figures come out: FVC, the total volume you can exhale, and FEV1, how much of it leaves in the first second.
Expected values for those depend on age, height, sex and other characteristics. Lung age inverts the calculation: instead of asking how your FEV1 compares to expected for someone your age, it asks what age a person of your height would have to be for your FEV1 to be their expected value.
A 45-year-old with reduced FEV1 might be told their lung age is 63. That is not a statement about tissue. It's a restatement of a spirometry result in more intuitive units.
Why it exists
Because it works as communication. "Your FEV1 is 68 percent of predicted" means very little to most people. "Your lungs are performing like someone twenty years older" lands.
There's evidence that presenting results this way improves smoking cessation rates compared with giving the raw numbers — which is a genuinely useful finding, and the main reason the concept is used in clinical practice at all.
Where it misleads
- It compresses different problems into one number. Obstructive and restrictive patterns are fundamentally different things, and a single "age" figure hides which you have. The FEV1/FVC ratio is what distinguishes them, and it doesn't survive the translation.
- It implies reversibility that may not exist. "Lung age 63" sounds like something you could wind back. Where the cause is structural — destroyed alveolar walls in emphysema — that damage is permanent. What quitting achieves is a slower rate of further decline, which is enormously valuable and is not the same as reversal.
- It invites exactly the wrong kind of marketing. If lung age can go up, surely a product can bring it down? No supplement has been shown to improve FEV1, and any product implying it reduces your lung age is making a measurable claim — one you could check with spirometry, and one nobody has demonstrated.
What to do with the number if you're given one
Take it seriously as a prompt and ask for the underlying figures. Specifically: your FEV1 as a percentage of predicted, your FVC, and the FEV1/FVC ratio. Those are what a clinician actually works from, and having them on record makes every future test interpretable.
One test locates you on the map. Two tests, separated by years, show you which way you are travelling — and direction is the far more valuable information. That is the argument for getting an early baseline on record, particularly for current or former smokers and for anyone whose working life has involved serious dust or fumes.
What genuinely moves the trajectory
Stopping smoking, at any age. Staying physically active, which doesn't enlarge healthy lungs but improves how efficiently you use them. Keeping vaccinations current, since infections can cause lasting damage. Treating diagnosed conditions properly. Reducing ongoing exposure where you can control it.
That list is short, unexciting, and does more than anything else available.
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