The common assumption that cutting back on cigarettes is nearly as good for your health as quitting just went up in smoke.

The British Medical Journal Wednesday published a review of research that shows smoking even one cigarette a day carries a surprisingly high risk of developing coronary heart disease (CHD) and stroke. This report is the first on light smoking and heart disease to combine the results from many studies—141 in total, involving nearly 13 million people. 

Risky Business

The results of the study were unexpected, according to lead study author Allan Hackshaw, Ph.D., deputy director of Cancer Research UK and UCL Cancer Trials Centre at University College London.

“Intuitively, smoking one cigarette instead of 20 [the number of cigarettes in a pack] should have about 1/20th the risk, and this is probably what many people feel is the case,” Hackshaw says.  

While smoking one cigarette a day did cut the risk of heart disease and stroke by about half compared to smoking a pack, that one-a-day risk was still significant. Men who smoked one cigarette a day had a 48 percent higher risk of CHD than people who never smoked, while women had a 57 percent increase. And in both men and women, researchers found around a 30 percent increase in the risk of stroke.

The take-home message for smokers: Any exposure to cigarettes is too much.

“Smokers should aim to quit instead of cutting down in order to avoid much of the risk of cardiovascular disease,” Hackshaw says.

A Disturbing Trend

The findings of this new study are particularly compelling considering the trend showing smokers are cutting back but not kicking the habit. For instance, those in the U.S. who light up less than 10 times a day increased from 16 percent to 27 percent between 2005 and 2014. The portion of smokers in the U.K. who consume one to five cigarettes a day has steadily risen from 18 percent to 24 percent between 2009 and 2014.

Less smoking is certainly better than more (“It does reduce harm,” says Hackshaw), but it’s no match for quitting.

“The non-linear relation between CHD and low cigarette consumption is not commonly known by the general public or health professionals, particularly those not involved in tobacco and health,” Hackshaw says.

For instance, in one 2015 study of nearly 25,000 U.S. adolescents published in the journal Pediatrics, only 35 percent of light smokers, defined as those who consume 10 or fewer cigarettes a day, considered their habits to be associated with “a lot of harm.”

How Smoking Hurts Your Heart

Smoking is at the top of the list of risk factors for heart disease, says Steve Nissen, M.D., chairman of the department of cardiovascular medicine at the Cleveland Clinic in Cleveland, Ohio.

“A lot of people equate smoking with lung cancer, but it’s actually heart disease where it causes the most mortality,” Nissen explains.

For example, one study found that about two thirds of CHD deaths that occur in smokers could be attributable to their habit.

Smoking takes a toll on the heart in a number of ways, according to the Centers for Disease Control and Prevention (CDC). Among other things, chemicals in cigarette smoke cause the cells that line blood vessels to become swollen and inflamed, which leads to narrowing of those vessels. The chemicals also cause the blood to thicken and form clots inside veins and arteries. Both changes can lead to a heart attack or stroke.

Much of this damage occurs relatively quickly, over only a few years, says Hackshaw at University College London.

“But this also represents good news for smokers, because it means that much of their increased risk for cardiovascular disease goes away quickly, too, once they stop smoking,” he explains.

Even long-time smokers can see rapid health improvements, according to the CDC. Within a year, heart attack risk drops dramatically; within five years, most smokers cut their risk of stroke to nearly that of a nonsmoker.

Kicking The Habit

If you’re one of the two-thirds of smokers who want to quit, gradually tapering your habit may have some benefit. Quitting cold turkey is rarely effective: Only 3 to 6 percent of smokers who make an unaided attempt to quit are still abstinent one year later.

Most people benefit from a number of strategies alone or in combination, according to pulmonologist Albert Rizzo, M.D., senior medical advisor to the American Lung Association. These include a reduction in the number of cigarettes they smoke, counseling, nicotine replacement options, or medication.

If you’re going to use a reduction strategy, think of it as one stop on the road to stopping smoking entirely.

And the less you smoke, the easier it is to stop.

“When you’re down to one cigarette a day, it’s likely you’re dealing with more of a habit than a chemical addiction to nicotine—there’s such a low amount of nicotine being consumed at that point,” says Rizzo.

To break the habit, substitute another hand-to-mouth action like picking up a toothpick or a cinnamon stick when you feel like reaching for a smoke, or distract yourself by talking a walk, calling a friend, or reading the news. For more help with smoking cessation, the American Lung Association offers free information at 800-LUNGUSA and