I'm manufacturing heart & lung support devices for a living. Look up the symptoms for COPD (chronic obstructive pulmonary disease). It's now the 4th most common cause of death worldwide (after cancer, strokes and coronary issues).

Basically, your lung dies a little bit over time, and loses its potential to remove CO2 from your blood. The biggest problem is the creeping progress. If you're not running marathons regularly, you wouldn't even notice if your lung capacity drops by 20%. 30, you're a bit short of breath when climbing stairs. Most people would assume they are just unfit.

But once you hit 40% and notice something's wrong, it's almost too late. Mind you, that can take 10-15 years, and usually only starts in your 30s, so you'll be 40-50 before noticeable symptoms begin.

But then the decline is increasing exponentially. You have trouble breathing - try sucking air through a wet tablecloth. That's how strenuous breathing will be (no joke, try it!!!). Additionally, the amount of CO2 in your blood will change its pH value, making your blood slightly acidic. The acidity kills your kidneys and affects your liver, and also decreases the elasticity of your blood vessels, increasing the risk of organ damage even more, contributes to formation of brain aneurysms, and also increases the risk of strokes.

Think that's all? Once your lung capacity is below 50%, you'll need mechanical ventilation - permanently. So they'll cut a hole into your airways and install one of those nifty adapters to hook you up to an oxygen bottle. Kinky, right? Comes with the downside of not being able to speak. And you'll have to drag 30lbs of equipment behind you wherever you go... On top of being in a weakened state that hardly permits you to carry 10lbs.

Consequently, you'll spend 95% of your remaining time on earth in bed, getting sores everywhere, needing help to take a shit for the rest of your life, all the while you can't communicate properly, feel like being continuously choked, and hurting all over.

Fun times ahead? Smoking/vaping is the leading cause of COPD. You probably just didn't hear about it because it's not an imminent killer. Cancer or stroke have better PR.

Oh, and there's no cure. You can't restore dead tissue. With lots of luck and care you can stop the progress where you're at. But you'll never, ever, recover a single percent of lung capacity unless you get a transplant (and elderly smokers usually don't make the cut...). And even if you did, transplant recipients often have a shortened lifespan due to complications resulting from the immunosuppressive medicine they have to take for the rest of their lives.

Good luck.