Smoking as little as one cigarette a day can still have serious health consequences.

Women who are light or moderate cigarette smokers — lighting up as little as once a day — still have an increased risk of sudden cardiac death, new research suggests.

"In our study we found small-to-moderate quantities, one to 14 cigarettes per day, were associated with almost a twofold higher risk of sudden cardiac death compared to women who never smoked," said lead researcher Dr. Roopinder Sandhu, an assistant professor of medicine at the University of Alberta, in Canada.

As the years passed, the risk climbed, even with light smoking.

The study appeared online Dec. 11 in the journal Circulation: Arrhythmia & Electrophysiology.

Sudden cardiac death is responsible for up to 400,000 deaths outside the hospital every year in the United States, according to the American Heart Association. Sudden cardiac arrest can occur when abnormal heart rhythms, or arrhythmias, cause the heart to stop pumping blood to the body.

Sandhu and colleagues followed more than 100,000 healthy women, all without known heart disease, stroke, or cancer at the study start, from the Nurses' Health Study. It began in 1976, and researchers have collected health information from the women twice a year, asking about habits and medical histories. Sandhu looked at records dating back to 1980.

During the 30 years of follow-up, 351 women died of sudden cardiac death. Sandhu, also a visiting scientist at Brigham & Women's Hospital, in Boston, looked at smoking patterns and found the link.

While the overall link between smoking and heart problems, as well as smoking and cancer and other health problems, has been known for a long time, experts knew less about how the quantity and duration of cigarette smoking affected risk.

At the study's start, 29 percent smoked, more than 26 percent had quit, and more than 44 percent never smoked.

Overall, those who were current smokers had more than double the risk of sudden cardiac death. Those who had one to 14 cigarettes a day had a nearly doubling of risk. Those who smoked 25 or more a day had more than triple the risk of sudden cardiac death.

While some may think it surprising that even light smoking can increase risk of sudden cardiac death, Sandhu said it makes sense. "There are acute effects of nicotine,'' she said, and these may lead to the abnormal heart rhythms and other problems that boost risk.

The risk of sudden cardiac death decreased after the women quit smoking. For women without heart disease, the risk dropped in fewer than five years. For those with heart disease who quit smoking, their risk of sudden cardiac death dropped to that of a nonsmoker, too, but it took 15 or 20 years.

The findings provide valuable new information, according to Dr. Gregg Fonarow, a professor of cardiology at the University of California, Los Angeles.

While the link between cigarette smoking and sudden cardiac death is well-established, he said, ''far less has been known about the relationship between number of cigarettes smoked, duration of smoking, and the risk of sudden cardiac death."

"This new study demonstrates that even low-level use of cigarettes, in the range of one to 14 cigarettes a day, is associated with a substantial increase in risk of sudden cardiac death in women," Fonarow said. "Even occasional cigarette smoking in social circumstances may unnecessarily increase women's risk of sudden unexpected death."

Study author Sandhu said there's no one best way to quit smoking: Each person needs to have a strategy tailored to them.

The study did not prove a causal relationship between light smoking and sudden cardiac death, although it did show an association.