There are a lot more factors involved besides just age, such as:
Were you exposed to second hand smoke growing up?
How old were you when you started smoking?
How much do you smoke?
How much smoke do you take in with each drag, and how deeply do you inhale?
Do you also smoke other things? (new studies show marijuana is harder on the lungs than tobacco).
Hopefully, you are asking because you have quit smoking, and just want to know if your lungs will return to normal. If you are asking because you are still smoking, and just want to know when you should count on having to quit, you are making the same mistake I made. and I have a clear plastic tube following me around the house now.
(Sorry if this sounds harsh or unsociable, but I am 52, have emphysema, and am still trying to get smoke free - as of this post, I have been smoke free for 26 hours).
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