Preliminary results from the largest U.S. survey of tobacco consumption show a high number of people use multiple products, adding key data to the debate on the role of e-cigarettes in reducing harm from tobacco.

The results of the study, released Thursday, showed 40 percent of tobacco consumers use multiple products, such as cigarillos, hookah and cigars. Half of all combinations involved e-cigarettes.

The Population Assessment of Tobacco and Health (PATH) Study of 46,000 people, begun in 2011, is designed to answer questions about the tobacco use and behavior and help shape industry regulation.

Public health officials have long questioned whether smokers attracted to e-cigarettes will use them to quit smoking or simply as an alternative for use in places where smoking is not allowed.

Data released on Thursday did not give definitive insight about why people are using different forms of tobacco. Andrew Hyland, scientific principal investigator on the study and chair of the department of health behavior at Roswell Park Cancer Institute, said they may be transitioning away from cigarettes, or they may be becoming more entrenched.

The study is expected to provide a wealth of information about tobacco use, smoking behavior and attitudes and will give the U.S. Food and Drug Administration data to reshape industry regulations.

"We were struck by the proportion of users that engaged in polyuse," Mitch Zeller, head of the Food and Drug Administration's tobacco division, said in an interview, referring to the use of multiple products.

Preliminary results were presented to an audience of scientists, researchers and industry representatives at the annual meeting of the Society for Research on Nicotine and Tobacco in Philadelphia.

The most common combination of products among youth and adults was cigarettes and e-cigarettes, data showed.

The results, to be gathered and disclosed over years, are expected to provide for tobacco the type of information that the decades-long Framingham Heart Study has provided about heart disease and its impact on public health.

Although the information about multi-product use is a start, more time will be needed to identify the reasons for such use, study organizers said.

"Is it a step towards people quitting, or are the hooks of nicotine just getting deeper," said Hyland.

The tobacco industry is rapidly changing with the popularity of electronic nicotine devices.

"The evolution that has taken place in the marketplace makes your head spin," Zeller said.