Smoking just one cigarette daily is associated with a "much greater than expected" increase in risk for coronary heart disease (CHD) and stroke, researchers conclude in The BMJ.

In a meta-analysis, the researchers analysed 141 prospective studies examining the association between smoking and CHD or stroke in millions of generally healthy people. Overall, compared with never-smoking, smoking one cigarette daily conferred significantly increased risks for both outcomes. Here are the findings based on the subset of studies that adjusted for multiple confounders (e.g., cholesterol, blood pressure):

• Women who smoked 1 cigarette daily had a 119% increased risk for CHD and a 46% increased risk for stroke.

• Men who smoked 1 cigarette daily had a 74% increased risk for CHD and a 30% increased risk for stroke.

• The risk from smoking 1 cigarette daily was about half that from smoking 20 cigarettes daily.