When you stop smoking, the benefits start immediately within minutes and hours. Your blood vessels start responding normally, you reduce the chances of a heart attack and those benefits just increase steadily over time. With your lungs though, is a bit different from the heart and blood vessels.
So you stop doing damage to the lungs as soon as you’ve stopped smoking. But if you’ve developed chronic obstructive pulmonary disease, where you’ve destroyed the very fabric of the lung, the best you can hope for, is that it doesn’t get any worse. In other words, as bad as it is then, that’s where it stops. And then, by taking exercise and medications. Building up your exercise capacity, the deficiency in your lungs can be compensated for by being more fit as long as you’re able to.
You should keep yourself from getting infections and your lungs from getting worse because of the infections. So the answer to that question depends on how much damage you’ve already done.
Dr Norman Swan, Physician and Journalist