Smoking just one cigarette a day doubles a woman's chance of sudden death, according to a large scale study that found you don't have to be a pack-a-day smoker to increase your risk of dying.
Canadian researchers studied 101,000 US nurses over 30 years and found that women who smoked — even if they only smoked between one and 14 cigarettes a day — were twice as likely to die of heart problems than women who had never lit up.
The research also found that when women quit, their risk drops within years.
During the 30-year study, 315 women died from sudden cardiac arrests, 75 of whom were current smokers, 148 were past smokers and 128 who had never smoked.
After accounting for heart risk factors such as high cholesterol, blood pressure and family history, the researchers concluded smokers were twice as likely to die, and their risk increased by eight percent every five years they continued smoking.
Smokers who quit saw their risk fall over 20 years until it was the same as someone who had never smoked.
"What this study really tells women is how important it is to stop smoking. The benefits in terms of sudden cardiac death reduction are there for all women, not just those with established heart disease," said study author Dr Roopinder Sandhu from the University of Alberta in Canada.
"It can be difficult to quit. It needs to be a long-term goal. It's not always easily achievable and it may take more than one attempt."
Professor Jim Tatoulis, chief medical adviser at the Heart Foundation, said women still aren't heeding the message.
"Although the overall rate of smoking in Australia has been falling, and now 19 percent of Australians are daily smokers, unfortunately the proportion of women that smoke is increasing," he said.
And the habit is starting young.
"One in 10 teenage girls smoke daily, compared to one in 17 teenage males, thus placing themselves at very high risk for heart attack, stroke and lung cancer as they age," Professor Tatoulis said.
"Most smokers know they should quit, but not all of them know that half of all smokers will die from a tobacco related disease, and half of those deaths will occur in middle age."
The good news is that quitting makes a big difference, quickly.
"There is a rapid decline in the risk of heart disease, stroke and other blood vessel disease, within one year of quitting, so it's never too late," Professor Tatoulis said.
The research was reported in the journal of the American Heart Association.