I'm not a doctor and certainly no authority on this topic. I've had some personal experience here and read many articles relating to this topic. The following is a summary of my understanding and therefore my opinion. I know, everyone has one...
The COPD group of destinations are not exclusive. One may lead to the other very easily (you smokers, don't settle for just one). Asthma contributes to the more severe bronchitis which can lead to the more severe emphysema. They're all very closely related. Allergies can help you into the chronic categories of COPD more easily if you smoke. It becomes chronic when you have two or more episodes in a 12 month period (this is a loose standard). Smoking easily turns a simple chest cold into bronchitis, routinely when combined with seasonal allergies.
The oxygen depraved environment of a smoker's body welcomes many other destinations as well. If you smoke you've already got one foot in the grave, so to speak.
A single episode of bronchitis damages your lungs to whatever degree. The more episodes, the more damage until you develop emphysema which is the lungs inability to function properly.
Smoking alone decreases the lungs capacity to function. Nature provides more than is required so this doesn't impact too greatly until other problems develop. If you quit early enough where the lost capacity can be regained you can regain some of what was lost and remove the catalyst that got you there. There's a chance you can get better and stop the progression of the damage.
There, I'm glad I got that out of my system. I was one of those that recovered. I still have my allergies but they don't progress beyond that, my body is healthy enough to contain it. I was one lucky stupid so and so. N.O.P.E.
[B]My Milage:[/B]
[B]My Quit Date: [/B]3/15/2007
[B]Smoke-Free Days:[/B] 163
[B]Cigarettes Not Smoked:[/B] 3,260
[B]Amount Saved:[/B] $684.60
[B]Life Gained:[/B]
[B]Days:[/B] 26 [B]Hrs:[/B] 7 [B]Mins:[/B] 30 [B]Seconds:[/B] 16