A new study published on January 24 by Allan Hackshaw and his colleague in the British Medical Journal reports that smoking even one cigarette per day carries a high risk for heart disease and stroke. One cigarette a day accounted for fully half of the excess heart disease risk associated with smoking 20 a day in men and one third of the risk in women.
To arrive at their results, Hackshaw and colleagues pooled data from 141 studies covering 5.6 million people for heart disease and 7.3 million people for stroke. The studies came from 20 different countries and covered a span of fifty years. Now we know the shape of the dose-response curve. Risk increases rapidly for a low-dose and more slowly after that. But it took 50 years and hundreds of thousands of deaths caused by smoking to arrive at this result.
A related editorial written by Canadian researcher Kenneth Johnson points out that second-hand smoking has also been shown to carry high risks for heart disease and stroke. Use of e-cigarettes and heat-not-burn cigarettes are also forms of low-dose smoking that produce ultrafine particles and many of the same toxic substances that cause adverse effects on the cardiovascular system in light smokers and passive smokers.
We do not have fifty years of experience with e-cigarettes and heat-not-burn cigarettes, nor should we wait for fifty years for definitive epidemiological evidence to emerge. We should recognize that these are forms of low-dose smoking that probably carry substantial increased risk for heart disease and stroke, similar to the risks of light cigarette smoking and passive smoking. A cautious policy response is recommended that would restrict marketing of these products and, as much as possible, limit their use to current smokers only.
The government of Canada is committed to achieving less than 5% tobacco use by 2035. Our new knowledge that even light smoking is hazardous makes it imperative that firm plans be put in place to achieve this goal. We should start by phasing out the most dangerous tobacco product of them all - combustible cigarettes.