Stolen Breath

It was unsettling enough that ABC anchorman Peter Jennings died of lung cancer just four months after announcing his diagnosis. Perhaps more distressing to the 90 million--plus smokers and former smokers out there was that Jennings swore off tobacco 20 years ago and was struck by the disease all the same. It's true that he had resumed smoking after the terrorist attacks in 2001, but he quit again. Can that first puff years ago start a fatal cascade of lung damage that can never be reversed? The answer is yes, and no.

Recently, British researchers wanted to see if there was a point of no return, at which it doesn't matter whether you quit. Their conclusion, published in BMJ (formerly the British Medical Journal) last year: timing is everything. The sooner you quit, the more damage you undo. A smoker who quits at age 50 reduces the risk of lung disease by half. Quitting by age 30 eliminates nearly all the smoking-related risk.

Hard on the heels of Jennings' death was the mind-numbing announcement that Dana Reeve, widow of actor Christopher Reeve and a nonsmoker, has lung cancer. It was a sobering reminder that about 15% of lung-cancer victims have never smoked.

In cases like those, the disease might simply be due to poor genetics, but it's worth remembering that the second leading cause of lung cancer in the U.S. is exposure to radon, a naturally occurring radioactive gas. The government estimates that 1 in 15 U.S. homes has radon levels that are too high. The best advice is to have your home tested. If you are worried that you might have symptoms of lung cancer-- such as a persistent cough, especially with blood-tinged sputum, or unintentional weight loss--get a checkup.

And, of course, if you don't smoke, don't start. If you do smoke, quit. Now is the best time.

Sanjay Gupta is a neurosurgeon and CNN medical correspondent