A review of 141 studies, published in the British Medical Journal found that even a single cigarette a day significantly increases the risk of developing coronary heart disease and stroke. Researchers found that smoking one cigarette a day brings about half the risk of smoking 20 per day. The study debunks the idea of a “safe level” of smoking and suggests that smokers should aim to quit, not cut down.

Image credits: Patrick Brinksma.

The idea that smoking is bad for you isn’t news to anyone — it’s about as established as it can get. Still, many myths about smoking are still floating about, refusing to disappear. Among them is the idea that if you “mostly” quit smoking — if you only smoke one or a few cigs a day — you get rid of most of the health hazards. That simply isn’t true, as study after study has shown. Now, University College London researchers have carried out a review of 141 such studies, finding that even one cigarette a day is still very hazardous.

“We have shown that a large proportion of the risk of coronary heart disease and stroke comes from smoking only a couple of cigarettes each day,” say the authors. “This probably comes as a surprise to many people. But there are also biological mechanisms that help explain the unexpectedly high risk associated with a low level of smoking.”

Cardiovascular diseases and not cancer are the main culprit when it comes to smoking, causing about 48% of smoking-related premature fatalities. Scientists compared the effect that smoking one cigarette a day has to smoking 20 cigarettes a day (a typical pack). Men who smoked 1 cig a day had 46% of the excess risk of heart disease and 41% of the excess risk of stroke associated with smoking 20 cigarettes per day, while for women the figures were 31% and 34% respectively.

“No safe level of smoking exists for cardiovascular disease,”  the researchers add in the study. “Smokers should quit instead of cutting down, using appropriate cessation aids if needed, to significantly reduce their risk of these two common major disorders.”

The take-home message for smokers is that “any exposure to cigarette smoke is too much,” they conclude.

Of the 1.22 billion smokers, 1 billion of them live in developing or transitional economies, and over 800 million are men. Eastern European countries such as Russia, Belarus, and Montenegro are the “leaders” when it comes to smoking averages. However, in developed countries, smoking has already peaked and is starting to decline, especially where anti-smoking legislation has been passed. For years, researchers have urged policy-makers to implement such legislation. In the US, adults aged 16 and above smoke an average of 1687.56 cigarettes a year.

Journal Reference: Allan Hackshaw et al. Low cigarette consumption and risk of coronary heart disease and stroke: meta-analysis of 141 cohort studies in 55 study reports. https://doi.org/10.1136/bmj.j5855

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