Let’s say that we have two men age 50. Both began smoking at age 15. However one of the men quit for five years from age 30 to 35 before picking up the habit again. Statistically, is the second man who quit for 5 years any better off health wise than the one who never stopped?
What if we substitute alcohol abuse, over eating, obesity, high blood pressure, or anything else. One guy took care of himself for five years but started back. Has he bought himself more time long term or is it insignificant?
I seem to recall from health education that every cigarette smoked does some cumulative and irreversible damage. So, with all other variables equal, the guy who stopped for 5 years should be better off. Whether that amount is material, I don’t know.
Also, what I’ve been told over time is that the scientific consensus is very uneasy with specifying a Quantum of Cigarette Damage, E.g. “Mary went out back for a smoke. She did 5 cowboys worth of damage.”, because of the nature of different people and how “hard” people smoke. So it may be the case that one of the men is just more genetically susceptible to smoking damage than the other, or maybe one of them inhales more deeply or something.
IIRC that’s true for some smoking related problems but not others. I want to say your risk of cancer goes down the longer you’ve gone without smoking, but your risk of emphysema will always remain the same…but I could be wrong about that.
Something else I heard is that ‘cutting down’ doesn’t really do any good in that the body actually needs to be smoke free to start repairing the damage. Again, that was a random piece of information I heard somewhere at some point in my life and it could be rubbish.
Having said all that, I would think that all else being exactly equal, someone who quit smoking for 5 years and then picked it up would have (5 x packs per day) Pack Years less under his belt. That’s gotta count for something.
In other words, two people, both 50, same genetic makeup, smoked the same amount, inhaled just as hard, ate the same, etc etc etc. Both smoked 2 packs per day. One is at 70 pack years the other is at 60 pack years.
I suppose that’s not a big difference and the older they get, the closer those numbers are going to be to each other.
Considering that factor alone is probably not useful. I’m guessing based on the studies I’ve seen that 5 years of non-smoking in the midst of a 50 year smoking habit is not going show a significant statistical difference. Whatever the cause of lung cancer is, 45-50 years of smoking is unquestionably sufficient to contribute the smoking related component. This is likely to be true of all of the health issues related to smoking.
There are a lot of smoking studies out there. Many of them use questionable methodology, but not all. Most of the questionable ones lead to similar results as those using more rigorous methodology. The worst ones are obviously outlandish, such as the claiming that smoking a single cigarette in a lifetime leads to a significant increase in smoking related disease. I’d concentrate on the overwhelming consensus that smoking greatly increases the risk of numerous health problems, and the more one smokes, the more likely it is for those problems to occur.
Hmm, that doesn’t quite match my understanding of how smoking causes cancer, though most of my knowledge of cancer comes from the molecular biology end of things. Anyways, my impression was that smoking usually causes very slow growing lung cancers, such that cancer rates start to increase about 20 years after people start smoking. In this case, a good amount of the cancer-causing damage has already been done. But quitting from 30-35 might still reduce the cumulative cancer risk from 50 onwards. Quitting at, say, 55 is probably too late to reduce the cancer risk but it will definitely reduce the emphysema risk.
That’s a good point, the difference is going to be relatively insignificant. Even if we assume perfectly linear damage that increases various risks, 45 years vs 50 years isn’t much of a difference. 0.9 relative risk reduction is pretty small, and you need a large and well-controlled study to detect any statistically significant differences between those two hypothetical populations. But such a study isn’t scientifically interesting – lots of smoking is bad, slightly less smoking is slightly less bad, which we already know from other methods.