Smoking just one cigarette a day carries half the risk for cardiovascular disease and stroke as a pack-a-day habit, according to research that concludes there is no safe level of smoking.

The study team analyzed data from 141 smaller studies to assess the risk of heart disease and stroke for people who smoked one, five or 20 cigarettes a day. Men who smoked one cigarette a day were 74 percent more likely to have heart disease and 30 percent more likely to have a stroke than men who never smoked at all, they report in The BMJ.

Women who smoked one cigarette daily were more than twice as likely to develop heart disease and 46 percent more likely to have a stroke than women who didn’t smoke.

“People who have always been light smokers will have a higher risk of cardiovascular disease than many of them expect,” said lead study author Allan Hackshaw of the Cancer Institute at University College London in the UK.

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