A national survey of U.S. middle and high school students finds that those who use tobacco or nicotine products are likely to also use more than one type of product.

About 15 percent of the adolescents reported smoking cigarettes, cigars, pipes, bidis, hookahs or water pipes, using dissolvable forms of tobacco or "vaping" e-cigarettes. And twice as many in that group used two or more of these product types compared to those who said they used only one.

“Our study really shows that kids are using more than one of these products at the same time,” said Youn Ok Lee of RTI International in Research Triangle Park, North Carolina, the report’s lead author.

Lee said there are many varieties of tobacco products available. And each type of product also has a diverse range of options, such as flavors.

“So we don’t really know a lot about how this range of products might affect kids’ use of tobacco,” she told Reuters Health.

Using data from a 2012 national survey of nearly 25,000 U.S. students, researchers found that about 7 percent reported using one tobacco product in the past 30 days. About 4 percent said they used two tobacco products in that time. Another 4 percent said they used three or more products.

“I was a little bit surprised by just how many kids were using more than one product,” Lee said. “Even more surprising was that using three or more products is more popular than using cigarettes alone.”

Overall, about 3 percent of kids exclusively used cigarettes and about 2 percent exclusively used cigars. Those products were the most popular and their use increased with age.

The study team also found that almost 1 percent of students reported exclusively using e-cigarettes, which contain no tobacco but deliver a vapor laced with nicotine, the addictive substance in tobacco.

That’s more than the 0.4 percent who reported using e-cigarettes in combination with traditional cigarettes.

The increasing popularity of e-cigarettes is a concern for U.S. health officials as use has tripled between 2013 and 2014 (see Reuters story of November 13, 2014 here: reut.rs/1zS6hCs).

Lee noted that the results don't tell why young people are using more than one form of tobacco, or how often the survey participants had used the products.

The researchers did find that being a boy, using flavored products, being dependent on nicotine, being receptive to advertising and having friends who used any tobacco products were all factors linked to an increased risk of using more than one product.

Policymakers and researchers should look at how these products affect tobacco use among middle and high school students, said Lee, because little is known about the influence of non-cigarette products.

Moreover, these products may create a public health issue by introducing people who would never have smoked cigarettes to nicotine, she said.

Lee emphasized that it’s important to look at all tobacco products together – not individually.