GENEVA – Women who smoke are 25 percent more likely than their male counterparts to develop heart disease, and the risk increases the longer women maintain the habit, according to research published in The Lancet journal on Thursday.

The higher risk could be because the toxins in cigarettes have a more potent effect on women than they do on men, researchers from the University of Minnesota and Johns Hopkins University wrote after surveying data from 4 million people in 86 studies spanning 45 years.

Women account for one in five of the world’s 1.1 billion smokers and almost one in three tobacco-related deaths, the authors wrote. Women are also taking up smoking faster than men in some developing nations where smoking has traditionally been a male habit, according to the World Health Organization.

“What makes the realization that women are at increased risk worrisome is that the tobacco industry views women as its growth market,” Matthew Steliga, a thoracic surgeon at the University of Arkansas for Medical Sciences; and Carolyn Dresler, director of Arkansas’s Tobacco Prevention and Cessation Program, wrote in an editorial accompanying the study.

Rachel Huxley, from the University of Minnesota, and Mark Woodward, from Johns Hopkins, scoured four online databases for studies about smoking and heart disease published between 1966 and 2010. They found 26 that contained information from 86 studies involving 3.9 million people around the world.

Compared with non-smokers, women who light up have a 25 percent greater chance of coronary heart disease than male smokers, independent of other risk factors, the authors found. The risk increases 2 percent every year they continue smoking, they wrote.