Even small amounts of smoking appears to nearly double a woman’s risk of sudden cardiac death, researchers are reporting.
Based on an analysis of more than 100,000 women enrolled in the massive U.S. Nurses’ Health Study, the new study is one of the first to attempt to quantify how much, and how long, women have to smoke in order to increase their sudden death risk, and how soon after quitting smoking the risk of early death begins to drop.
Researchers found that “even small-to-moderate” amounts of cigarettes smoked daily — one to 14 per day — were associated with an almost two-fold increase in sudden death.
Not surprisingly, the longer women smoked the higher their risk. Every five years of continued smoking was associated with an eight-per-cent increase in sudden cardiac death, said lead author Dr. Roopinder Sandhu, a cardiac electrophysiologist at the University of Alberta’s Mazankowski Heart Institute in Edmonton. Sandhu performed the research in Boston, where he is also a visiting scientist at Brigham and Women’s Hospital.
Most sudden cardiac deaths occur in people without known heart disease. Abnormal heart rhythms are the most common cause. Unless an electric shock is delivered the person can die within minutes. Each year up to 40,000 Canadians die of sudden cardiac arrest, according to the Heart and Stroke Foundation.
Nicotine may trigger life-threatening arrhythmias in several ways, Sandhu said. Nicotine can promote plaque build up in heart vessels and stimulate the release of epinephrine and norepinephrine, stress hormones that increase heart rate. It can decrease oxygen supply to the blood and make blood platelets stickier, increasing the risk of a blood clot.
For the study, researchers looked at the association between smoking and the risk of sudden cardiac death among 101,018 women enrolled in the nurses’ study who were free of known cardiovascular disease when the study began in 1980. Every two years the women, who were aged 30 to 55 at the study’s start, received a follow-up questionnaire about their medical history, cardiovascular risk factors (including their current smoking status) and any newly diagnosed medical conditions.
During 30 years of follow-up, the researchers identified 351 women who had died of sudden cardiac death.
Compared to never smokers, smokers had a 2.44-fold increased risk of sudden death after researchers took known risk factors, such as age, diabetes, high blood pressure and high cholesterol into account.
Women who reported smoking one to 14 cigarettes daily had a 1.84-fold increase in sudden cardiac death risk. Women who smoked 25 cigarettes or more had more than a three-fold increased risk of sudden death compared to never smokers.
The longer women smoked, the higher their risk: Women who smoked for more than 35 years were three times more likely to die during the follow-up than women who never smoked.
For women who quit smoking, their risk of sudden death dropped to that of nonsmoker after 20 years of stopping.
The study involved relatively healthy Caucasian women.
The researchers grouped cigarettes smoked per day into three categories: one to 14, 15 to 24 and 25 or more. “So it’s hard to differentiate the (risk from) one cigarette from the 14, but it’s still a small number,” Sandhu said.
Still, the findings could be sobering news for people who think that smoking only when they drink alcohol is mostly harmless.
“I think people have this misconception that a small amount of cigarette smoking is not harmful. Our study suggests it may be harmful and it may increase your risk of sudden cardiac death,” Sandhu said.
“But smoking is a modifiable risk factor. We should try to be aggressive with strategies for smoking cessation for every woman who is smoking.”