In more than 30 years of smoking, 49-year-old Kathy Barwick says she's tried to quit but failed several times.

"When I first began to smoke, it used to make me physically ill and I still kept up with it," said Barwick. "I used to pray, 'Please don't let me get sick and I swear I won't smoke again.' And yet I did."

A new Harvard study, published in the latest Journal of the American Medical Association shows women who are able to successfully quit can decrease their risk of dying from serious disease within just five years of smoking their last cigarette.

Doctors say it's a big wake-up call for smokers who've been in denial about quitting.

"The argument that I'm 65 and I've been smoking for the last 40 years, why stop now? Well if you want to see your granddaughter get married it probably is a good idea to stop smoking now," said Dr. John Coppola of St. Vincent's Medical Center in New York City. There was a significant decrease in the events of cardiac heart attacks and strokes and also a decrease in the incidences of lung cancer. So it's never too late to stop smoking."

Doctors say what's significant about the Harvard study was just how large it was. It involved about 100,000 women whose mortality rates were tracked from 1980 through 2004.

Within the first five years of quitting, there was a 21 percent decrease in risk of dying from lung cancer. Risk of dying from heart disease was cut in half. Within 20 years of quitting, some women's risk of dying from heart disease was equal to that of women who'd never smoked.

Another huge aspect of this study - some of the women who'd smoked for decades still saw some major health benefits when they finally quit smoking.

"The body has a remarkable ability to repair itself, and over the ensuing years you start to repair the damages that have been done to the blood vessels from cigarette smoking," said Coppola. "That repair process is pretty rapid. That's why you see that very sharp drop off in heart attacks in the first five years. To completely repair it takes a bit longer.

Knowing finally kicking the habit for good could potentially add years to her life has Barwick wanting to finally be able to do it this time around.

"The main reason I want to quit and I'm really going to try and this is for Kristen, my daughter," said Barwick. "I would love to see my grandchildren. That is the main reason."