No Amount of Cigarettes Is Safe
The authors of a new systematic review and meta-analysis have found that smoking even 1 cigarette per day significantly increases one’s risk for coronary heart disease (CHD) and stroke, emphasizing that there is no safe level of smoking for cardiovascular disease (CVD).
For their analysis, researchers identified and evaluated 141 cohort studies in 55 publications that were published between 1946 and May 2015. All studies included in the analysis had reported at least 50 events, as well as hazard ratios or relative risks compared with never-smokers or age-specific incidence in regard to CHD or stroke risk.
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Meta-analyses Of Observational Studies in Epidemiology (MOOSE) guidelines were followed, and relative risk for smoking 1, 5, or 20 cigarettes per day was estimated via regression modeling.
Findings indicated that, in men, the pooled relative risk for CHD was 1.48 and 2.04 among all studies for smoking 1 and 20 cigarettes per day, respectively. The corresponding pooled relative risk in women was 1.57 and 2.84, respectively. Notably, men and women who smoked 1 cigarette per day had 46% and 31% of the excess risk for CHD compared with those who smoked 20 cigarettes per day, respectively.
In regard to stroke risk, men who smoked 1 and 20 cigarettes per day had pooled relative risk of 1.25 and 1.64, respectively. In women, the corresponding pooled relative risk was 1.31 and 2.16. Men and women who smoked 1 cigarette per day had an excess risk for stroke of 41% and 34%, respectively.
The researchers also calculated relative risks for men and women in regard to CHD and stroke risk, noting that relative risks were typically higher in women than in men.
“Smoking only about one cigarette per day carries a risk of developing coronary heart disease and stroke much greater than expected: around half that for people who smoke 20 per day,” the researchers concluded. “No safe level of smoking exists for cardiovascular disease. Smokers should aim to quit instead of cutting down to significantly reduce their risk of these two common major disorders.”
—Christina Vogt
Reference:
Hackshaw A, Morris JK, Boniface S, Tang JL, Milenković D. Low cigarette consumption and risk of coronary heart disease and stroke: meta-analysis of 141 cohort studies in 55 study reports [Published online January 24, 2018]. BMJ. https://doi.org/10.1136/bmj.j5855.